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sqlite/src/pager.c
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/*
** 2001 September 15
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
** This is the implementation of the page cache subsystem or "pager".
**
** The pager is used to access a database disk file. It implements
** atomic commit and rollback through the use of a journal file that
** is separate from the database file. The pager also implements file
** locking to prevent two processes from writing the same database
** file simultaneously, or one process from reading the database while
** another is writing.
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
#include "wal.h"
/******************* NOTES ON THE DESIGN OF THE PAGER ************************
**
** This comment block describes invariants that hold when using a rollback
** journal. These invariants do not apply for journal_mode=WAL,
** journal_mode=MEMORY, or journal_mode=OFF.
**
** Within this comment block, a page is deemed to have been synced
** automatically as soon as it is written when PRAGMA synchronous=OFF.
** Otherwise, the page is not synced until the xSync method of the VFS
** is called successfully on the file containing the page.
**
** Definition: A page of the database file is said to be "overwriteable" if
** one or more of the following are true about the page:
**
** (a) The original content of the page as it was at the beginning of
** the transaction has been written into the rollback journal and
** synced.
**
** (b) The page was a freelist leaf page at the start of the transaction.
**
** (c) The page number is greater than the largest page that existed in
** the database file at the start of the transaction.
**
** (1) A page of the database file is never overwritten unless one of the
** following are true:
**
** (a) The page and all other pages on the same sector are overwriteable.
**
** (b) The atomic page write optimization is enabled, and the entire
** transaction other than the update of the transaction sequence
** number consists of a single page change.
**
** (2) The content of a page written into the rollback journal exactly matches
** both the content in the database when the rollback journal was written
** and the content in the database at the beginning of the current
** transaction.
**
** (3) Writes to the database file are an integer multiple of the page size
** in length and are aligned on a page boundary.
**
** (4) Reads from the database file are either aligned on a page boundary and
** an integer multiple of the page size in length or are taken from the
** first 100 bytes of the database file.
**
** (5) All writes to the database file are synced prior to the rollback journal
** being deleted, truncated, or zeroed.
**
** (6) If a super-journal file is used, then all writes to the database file
** are synced prior to the super-journal being deleted.
**
** Definition: Two databases (or the same database at two points it time)
** are said to be "logically equivalent" if they give the same answer to
** all queries. Note in particular the content of freelist leaf
** pages can be changed arbitrarily without affecting the logical equivalence
** of the database.
**
** (7) At any time, if any subset, including the empty set and the total set,
** of the unsynced changes to a rollback journal are removed and the
** journal is rolled back, the resulting database file will be logically
** equivalent to the database file at the beginning of the transaction.
**
** (8) When a transaction is rolled back, the xTruncate method of the VFS
** is called to restore the database file to the same size it was at
** the beginning of the transaction. (In some VFSes, the xTruncate
** method is a no-op, but that does not change the fact the SQLite will
** invoke it.)
**
** (9) Whenever the database file is modified, at least one bit in the range
** of bytes from 24 through 39 inclusive will be changed prior to releasing
** the EXCLUSIVE lock, thus signaling other connections on the same
** database to flush their caches.
**
** (10) The pattern of bits in bytes 24 through 39 shall not repeat in less
** than one billion transactions.
**
** (11) A database file is well-formed at the beginning and at the conclusion
** of every transaction.
**
** (12) An EXCLUSIVE lock is held on the database file when writing to
** the database file.
**
** (13) A SHARED lock is held on the database file while reading any
** content out of the database file.
**
******************************************************************************/
/*
** Macros for troubleshooting. Normally turned off
*/
#if 0
int sqlite3PagerTrace=1; /* True to enable tracing */
#define sqlite3DebugPrintf printf
#define PAGERTRACE(X) if( sqlite3PagerTrace ){ sqlite3DebugPrintf X; }
#else
#define PAGERTRACE(X)
#endif
/*
** The following two macros are used within the PAGERTRACE() macros above
** to print out file-descriptors.
**
** PAGERID() takes a pointer to a Pager struct as its argument. The
** associated file-descriptor is returned. FILEHANDLEID() takes an sqlite3_file
** struct as its argument.
*/
#define PAGERID(p) (SQLITE_PTR_TO_INT(p->fd))
#define FILEHANDLEID(fd) (SQLITE_PTR_TO_INT(fd))
/*
** The Pager.eState variable stores the current 'state' of a pager. A
** pager may be in any one of the seven states shown in the following
** state diagram.
**
** OPEN <------+------+
** | | |
** V | |
** +---------> READER-------+ |
** | | |
** | V |
** |<-------WRITER_LOCKED------> ERROR
** | | ^
** | V |
** |<------WRITER_CACHEMOD-------->|
** | | |
** | V |
** |<-------WRITER_DBMOD---------->|
** | | |
** | V |
** +<------WRITER_FINISHED-------->+
**
**
** List of state transitions and the C [function] that performs each:
**
** OPEN -> READER [sqlite3PagerSharedLock]
** READER -> OPEN [pager_unlock]
**
** READER -> WRITER_LOCKED [sqlite3PagerBegin]
** WRITER_LOCKED -> WRITER_CACHEMOD [pager_open_journal]
** WRITER_CACHEMOD -> WRITER_DBMOD [syncJournal]
** WRITER_DBMOD -> WRITER_FINISHED [sqlite3PagerCommitPhaseOne]
** WRITER_*** -> READER [pager_end_transaction]
**
** WRITER_*** -> ERROR [pager_error]
** ERROR -> OPEN [pager_unlock]
**
**
** OPEN:
**
** The pager starts up in this state. Nothing is guaranteed in this
** state - the file may or may not be locked and the database size is
** unknown. The database may not be read or written.
**
** * No read or write transaction is active.
** * Any lock, or no lock at all, may be held on the database file.
** * The dbSize, dbOrigSize and dbFileSize variables may not be trusted.
**
** READER:
**
** In this state all the requirements for reading the database in
** rollback (non-WAL) mode are met. Unless the pager is (or recently
** was) in exclusive-locking mode, a user-level read transaction is
** open. The database size is known in this state.
**
** A connection running with locking_mode=normal enters this state when
** it opens a read-transaction on the database and returns to state
** OPEN after the read-transaction is completed. However a connection
** running in locking_mode=exclusive (including temp databases) remains in
** this state even after the read-transaction is closed. The only way
** a locking_mode=exclusive connection can transition from READER to OPEN
** is via the ERROR state (see below).
**
** * A read transaction may be active (but a write-transaction cannot).
** * A SHARED or greater lock is held on the database file.
** * The dbSize variable may be trusted (even if a user-level read
** transaction is not active). The dbOrigSize and dbFileSize variables
** may not be trusted at this point.
** * If the database is a WAL database, then the WAL connection is open.
** * Even if a read-transaction is not open, it is guaranteed that
** there is no hot-journal in the file-system.
**
** WRITER_LOCKED:
**
** The pager moves to this state from READER when a write-transaction
** is first opened on the database. In WRITER_LOCKED state, all locks
** required to start a write-transaction are held, but no actual
** modifications to the cache or database have taken place.
**
** In rollback mode, a RESERVED or (if the transaction was opened with
** BEGIN EXCLUSIVE) EXCLUSIVE lock is obtained on the database file when
** moving to this state, but the journal file is not written to or opened
** to in this state. If the transaction is committed or rolled back while
** in WRITER_LOCKED state, all that is required is to unlock the database
** file.
**
** IN WAL mode, WalBeginWriteTransaction() is called to lock the log file.
** If the connection is running with locking_mode=exclusive, an attempt
** is made to obtain an EXCLUSIVE lock on the database file.
**
** * A write transaction is active.
** * If the connection is open in rollback-mode, a RESERVED or greater
** lock is held on the database file.
** * If the connection is open in WAL-mode, a WAL write transaction
** is open (i.e. sqlite3WalBeginWriteTransaction() has been successfully
** called).
** * The dbSize, dbOrigSize and dbFileSize variables are all valid.
** * The contents of the pager cache have not been modified.
** * The journal file may or may not be open.
** * Nothing (not even the first header) has been written to the journal.
**
** WRITER_CACHEMOD:
**
** A pager moves from WRITER_LOCKED state to this state when a page is
** first modified by the upper layer. In rollback mode the journal file
** is opened (if it is not already open) and a header written to the
** start of it. The database file on disk has not been modified.
**
** * A write transaction is active.
** * A RESERVED or greater lock is held on the database file.
** * The journal file is open and the first header has been written
** to it, but the header has not been synced to disk.
** * The contents of the page cache have been modified.
**
** WRITER_DBMOD:
**
** The pager transitions from WRITER_CACHEMOD into WRITER_DBMOD state
** when it modifies the contents of the database file. WAL connections
** never enter this state (since they do not modify the database file,
** just the log file).
**
** * A write transaction is active.
** * An EXCLUSIVE or greater lock is held on the database file.
** * The journal file is open and the first header has been written
** and synced to disk.
** * The contents of the page cache have been modified (and possibly
** written to disk).
**
** WRITER_FINISHED:
**
** It is not possible for a WAL connection to enter this state.
**
** A rollback-mode pager changes to WRITER_FINISHED state from WRITER_DBMOD
** state after the entire transaction has been successfully written into the
** database file. In this state the transaction may be committed simply
** by finalizing the journal file. Once in WRITER_FINISHED state, it is
** not possible to modify the database further. At this point, the upper
** layer must either commit or rollback the transaction.
**
** * A write transaction is active.
** * An EXCLUSIVE or greater lock is held on the database file.
** * All writing and syncing of journal and database data has finished.
** If no error occurred, all that remains is to finalize the journal to
** commit the transaction. If an error did occur, the caller will need
** to rollback the transaction.
**
** ERROR:
**
** The ERROR state is entered when an IO or disk-full error (including
** SQLITE_IOERR_NOMEM) occurs at a point in the code that makes it
** difficult to be sure that the in-memory pager state (cache contents,
** db size etc.) are consistent with the contents of the file-system.
**
** Temporary pager files may enter the ERROR state, but in-memory pagers
** cannot.
**
** For example, if an IO error occurs while performing a rollback,
** the contents of the page-cache may be left in an inconsistent state.
** At this point it would be dangerous to change back to READER state
** (as usually happens after a rollback). Any subsequent readers might
** report database corruption (due to the inconsistent cache), and if
** they upgrade to writers, they may inadvertently corrupt the database
** file. To avoid this hazard, the pager switches into the ERROR state
** instead of READER following such an error.
**
** Once it has entered the ERROR state, any attempt to use the pager
** to read or write data returns an error. Eventually, once all
** outstanding transactions have been abandoned, the pager is able to
** transition back to OPEN state, discarding the contents of the
** page-cache and any other in-memory state at the same time. Everything
** is reloaded from disk (and, if necessary, hot-journal rollback performed)
** when a read-transaction is next opened on the pager (transitioning
** the pager into READER state). At that point the system has recovered
** from the error.
**
** Specifically, the pager jumps into the ERROR state if:
**
** 1. An error occurs while attempting a rollback. This happens in
** function sqlite3PagerRollback().
**
** 2. An error occurs while attempting to finalize a journal file
** following a commit in function sqlite3PagerCommitPhaseTwo().
**
** 3. An error occurs while attempting to write to the journal or
** database file in function pagerStress() in order to free up
** memory.
**
** In other cases, the error is returned to the b-tree layer. The b-tree
** layer then attempts a rollback operation. If the error condition
** persists, the pager enters the ERROR state via condition (1) above.
**
** Condition (3) is necessary because it can be triggered by a read-only
** statement executed within a transaction. In this case, if the error
** code were simply returned to the user, the b-tree layer would not
** automatically attempt a rollback, as it assumes that an error in a
** read-only statement cannot leave the pager in an internally inconsistent
** state.
**
** * The Pager.errCode variable is set to something other than SQLITE_OK.
** * There are one or more outstanding references to pages (after the
** last reference is dropped the pager should move back to OPEN state).
** * The pager is not an in-memory pager.
**
**
** Notes:
**
** * A pager is never in WRITER_DBMOD or WRITER_FINISHED state if the
** connection is open in WAL mode. A WAL connection is always in one
** of the first four states.
**
** * Normally, a connection open in exclusive mode is never in PAGER_OPEN
** state. There are two exceptions: immediately after exclusive-mode has
** been turned on (and before any read or write transactions are
** executed), and when the pager is leaving the "error state".
**
** * See also: assert_pager_state().
*/
#define PAGER_OPEN 0
#define PAGER_READER 1
#define PAGER_WRITER_LOCKED 2
#define PAGER_WRITER_CACHEMOD 3
#define PAGER_WRITER_DBMOD 4
#define PAGER_WRITER_FINISHED 5
#define PAGER_ERROR 6
/*
** The Pager.eLock variable is almost always set to one of the
** following locking-states, according to the lock currently held on
** the database file: NO_LOCK, SHARED_LOCK, RESERVED_LOCK or EXCLUSIVE_LOCK.
** This variable is kept up to date as locks are taken and released by
** the pagerLockDb() and pagerUnlockDb() wrappers.
**
** If the VFS xLock() or xUnlock() returns an error other than SQLITE_BUSY
** (i.e. one of the SQLITE_IOERR subtypes), it is not clear whether or not
** the operation was successful. In these circumstances pagerLockDb() and
** pagerUnlockDb() take a conservative approach - eLock is always updated
** when unlocking the file, and only updated when locking the file if the
** VFS call is successful. This way, the Pager.eLock variable may be set
** to a less exclusive (lower) value than the lock that is actually held
** at the system level, but it is never set to a more exclusive value.
**
** This is usually safe. If an xUnlock fails or appears to fail, there may
** be a few redundant xLock() calls or a lock may be held for longer than
** required, but nothing really goes wrong.
**
** The exception is when the database file is unlocked as the pager moves
** from ERROR to OPEN state. At this point there may be a hot-journal file
** in the file-system that needs to be rolled back (as part of an OPEN->SHARED
** transition, by the same pager or any other). If the call to xUnlock()
** fails at this point and the pager is left holding an EXCLUSIVE lock, this
** can confuse the call to xCheckReservedLock() call made later as part
** of hot-journal detection.
**
** xCheckReservedLock() is defined as returning true "if there is a RESERVED
** lock held by this process or any others". So xCheckReservedLock may
** return true because the caller itself is holding an EXCLUSIVE lock (but
** doesn't know it because of a previous error in xUnlock). If this happens
** a hot-journal may be mistaken for a journal being created by an active
** transaction in another process, causing SQLite to read from the database
** without rolling it back.
**
** To work around this, if a call to xUnlock() fails when unlocking the
** database in the ERROR state, Pager.eLock is set to UNKNOWN_LOCK. It
** is only changed back to a real locking state after a successful call
** to xLock(EXCLUSIVE). Also, the code to do the OPEN->SHARED state transition
** omits the check for a hot-journal if Pager.eLock is set to UNKNOWN_LOCK
** lock. Instead, it assumes a hot-journal exists and obtains an EXCLUSIVE
** lock on the database file before attempting to roll it back. See function
** PagerSharedLock() for more detail.
**
** Pager.eLock may only be set to UNKNOWN_LOCK when the pager is in
** PAGER_OPEN state.
*/
#define UNKNOWN_LOCK (EXCLUSIVE_LOCK+1)
/*
** The maximum allowed sector size. 64KiB. If the xSectorsize() method
** returns a value larger than this, then MAX_SECTOR_SIZE is used instead.
** This could conceivably cause corruption following a power failure on
** such a system. This is currently an undocumented limit.
*/
#define MAX_SECTOR_SIZE 0x10000
/*
** An instance of the following structure is allocated for each active
** savepoint and statement transaction in the system. All such structures
** are stored in the Pager.aSavepoint[] array, which is allocated and
** resized using sqlite3Realloc().
**
** When a savepoint is created, the PagerSavepoint.iHdrOffset field is
** set to 0. If a journal-header is written into the main journal while
** the savepoint is active, then iHdrOffset is set to the byte offset
** immediately following the last journal record written into the main
** journal before the journal-header. This is required during savepoint
** rollback (see pagerPlaybackSavepoint()).
*/
typedef struct PagerSavepoint PagerSavepoint;
struct PagerSavepoint {
i64 iOffset; /* Starting offset in main journal */
i64 iHdrOffset; /* See above */
Bitvec *pInSavepoint; /* Set of pages in this savepoint */
Pgno nOrig; /* Original number of pages in file */
Pgno iSubRec; /* Index of first record in sub-journal */
int bTruncateOnRelease; /* If stmt journal may be truncated on RELEASE */
#ifndef SQLITE_OMIT_WAL
u32 aWalData[WAL_SAVEPOINT_NDATA]; /* WAL savepoint context */
#endif
};
/*
** Bits of the Pager.doNotSpill flag. See further description below.
*/
#define SPILLFLAG_OFF 0x01 /* Never spill cache. Set via pragma */
#define SPILLFLAG_ROLLBACK 0x02 /* Current rolling back, so do not spill */
#define SPILLFLAG_NOSYNC 0x04 /* Spill is ok, but do not sync */
/*
** An open page cache is an instance of struct Pager. A description of
** some of the more important member variables follows:
**
** eState
**
** The current 'state' of the pager object. See the comment and state
** diagram above for a description of the pager state.
**
** eLock
**
** For a real on-disk database, the current lock held on the database file -
** NO_LOCK, SHARED_LOCK, RESERVED_LOCK or EXCLUSIVE_LOCK.
**
** For a temporary or in-memory database (neither of which require any
** locks), this variable is always set to EXCLUSIVE_LOCK. Since such
** databases always have Pager.exclusiveMode==1, this tricks the pager
** logic into thinking that it already has all the locks it will ever
** need (and no reason to release them).
**
** In some (obscure) circumstances, this variable may also be set to
** UNKNOWN_LOCK. See the comment above the #define of UNKNOWN_LOCK for
** details.
**
** changeCountDone
**
** This boolean variable is used to make sure that the change-counter
** (the 4-byte header field at byte offset 24 of the database file) is
** not updated more often than necessary.
**
** It is set to true when the change-counter field is updated, which
** can only happen if an exclusive lock is held on the database file.
** It is cleared (set to false) whenever an exclusive lock is
** relinquished on the database file. Each time a transaction is committed,
** The changeCountDone flag is inspected. If it is true, the work of
** updating the change-counter is omitted for the current transaction.
**
** This mechanism means that when running in exclusive mode, a connection
** need only update the change-counter once, for the first transaction
** committed.
**
** setSuper
**
** When PagerCommitPhaseOne() is called to commit a transaction, it may
** (or may not) specify a super-journal name to be written into the
** journal file before it is synced to disk.
**
** Whether or not a journal file contains a super-journal pointer affects
** the way in which the journal file is finalized after the transaction is
** committed or rolled back when running in "journal_mode=PERSIST" mode.
** If a journal file does not contain a super-journal pointer, it is
** finalized by overwriting the first journal header with zeroes. If
** it does contain a super-journal pointer the journal file is finalized
** by truncating it to zero bytes, just as if the connection were
** running in "journal_mode=truncate" mode.
**
** Journal files that contain super-journal pointers cannot be finalized
** simply by overwriting the first journal-header with zeroes, as the
** super-journal pointer could interfere with hot-journal rollback of any
** subsequently interrupted transaction that reuses the journal file.
**
** The flag is cleared as soon as the journal file is finalized (either
** by PagerCommitPhaseTwo or PagerRollback). If an IO error prevents the
** journal file from being successfully finalized, the setSuper flag
** is cleared anyway (and the pager will move to ERROR state).
**
** doNotSpill
**
** This variables control the behavior of cache-spills (calls made by
** the pcache module to the pagerStress() routine to write cached data
** to the file-system in order to free up memory).
**
** When bits SPILLFLAG_OFF or SPILLFLAG_ROLLBACK of doNotSpill are set,
** writing to the database from pagerStress() is disabled altogether.
** The SPILLFLAG_ROLLBACK case is done in a very obscure case that
** comes up during savepoint rollback that requires the pcache module
** to allocate a new page to prevent the journal file from being written
** while it is being traversed by code in pager_playback(). The SPILLFLAG_OFF
** case is a user preference.
**
** If the SPILLFLAG_NOSYNC bit is set, writing to the database from
** pagerStress() is permitted, but syncing the journal file is not.
** This flag is set by sqlite3PagerWrite() when the file-system sector-size
** is larger than the database page-size in order to prevent a journal sync
** from happening in between the journalling of two pages on the same sector.
**
** subjInMemory
**
** This is a boolean variable. If true, then any required sub-journal
** is opened as an in-memory journal file. If false, then in-memory
** sub-journals are only used for in-memory pager files.
**
** This variable is updated by the upper layer each time a new
** write-transaction is opened.
**
** dbSize, dbOrigSize, dbFileSize
**
** Variable dbSize is set to the number of pages in the database file.
** It is valid in PAGER_READER and higher states (all states except for
** OPEN and ERROR).
**
** dbSize is set based on the size of the database file, which may be
** larger than the size of the database (the value stored at offset
** 28 of the database header by the btree). If the size of the file
** is not an integer multiple of the page-size, the value stored in
** dbSize is rounded down (i.e. a 5KB file with 2K page-size has dbSize==2).
** Except, any file that is greater than 0 bytes in size is considered
** to have at least one page. (i.e. a 1KB file with 2K page-size leads
** to dbSize==1).
**
** During a write-transaction, if pages with page-numbers greater than
** dbSize are modified in the cache, dbSize is updated accordingly.
** Similarly, if the database is truncated using PagerTruncateImage(),
** dbSize is updated.
**
** Variables dbOrigSize and dbFileSize are valid in states
** PAGER_WRITER_LOCKED and higher. dbOrigSize is a copy of the dbSize
** variable at the start of the transaction. It is used during rollback,
** and to determine whether or not pages need to be journalled before
** being modified.
**
** Throughout a write-transaction, dbFileSize contains the size of
** the file on disk in pages. It is set to a copy of dbSize when the
** write-transaction is first opened, and updated when VFS calls are made
** to write or truncate the database file on disk.
**
** The only reason the dbFileSize variable is required is to suppress
** unnecessary calls to xTruncate() after committing a transaction. If,
** when a transaction is committed, the dbFileSize variable indicates
** that the database file is larger than the database image (Pager.dbSize),
** pager_truncate() is called. The pager_truncate() call uses xFilesize()
** to measure the database file on disk, and then truncates it if required.
** dbFileSize is not used when rolling back a transaction. In this case
** pager_truncate() is called unconditionally (which means there may be
** a call to xFilesize() that is not strictly required). In either case,
** pager_truncate() may cause the file to become smaller or larger.
**
** dbHintSize
**
** The dbHintSize variable is used to limit the number of calls made to
** the VFS xFileControl(FCNTL_SIZE_HINT) method.
**
** dbHintSize is set to a copy of the dbSize variable when a
** write-transaction is opened (at the same time as dbFileSize and
** dbOrigSize). If the xFileControl(FCNTL_SIZE_HINT) method is called,
** dbHintSize is increased to the number of pages that correspond to the
** size-hint passed to the method call. See pager_write_pagelist() for
** details.
**
** errCode
**
** The Pager.errCode variable is only ever used in PAGER_ERROR state. It
** is set to zero in all other states. In PAGER_ERROR state, Pager.errCode
** is always set to SQLITE_FULL, SQLITE_IOERR or one of the SQLITE_IOERR_XXX
** sub-codes.
**
** syncFlags, walSyncFlags
**
** syncFlags is either SQLITE_SYNC_NORMAL (0x02) or SQLITE_SYNC_FULL (0x03).
** syncFlags is used for rollback mode. walSyncFlags is used for WAL mode
** and contains the flags used to sync the checkpoint operations in the
** lower two bits, and sync flags used for transaction commits in the WAL
** file in bits 0x04 and 0x08. In other words, to get the correct sync flags
** for checkpoint operations, use (walSyncFlags&0x03) and to get the correct
** sync flags for transaction commit, use ((walSyncFlags>>2)&0x03). Note
** that with synchronous=NORMAL in WAL mode, transaction commit is not synced
** meaning that the 0x04 and 0x08 bits are both zero.
*/
struct Pager {
sqlite3_vfs *pVfs; /* OS functions to use for IO */
u8 exclusiveMode; /* Boolean. True if locking_mode==EXCLUSIVE */
u8 journalMode; /* One of the PAGER_JOURNALMODE_* values */
u8 useJournal; /* Use a rollback journal on this file */
u8 noSync; /* Do not sync the journal if true */
u8 fullSync; /* Do extra syncs of the journal for robustness */
u8 extraSync; /* sync directory after journal delete */
u8 syncFlags; /* SYNC_NORMAL or SYNC_FULL otherwise */
u8 walSyncFlags; /* See description above */
u8 tempFile; /* zFilename is a temporary or immutable file */
u8 noLock; /* Do not lock (except in WAL mode) */
u8 readOnly; /* True for a read-only database */
u8 memDb; /* True to inhibit all file I/O */
u8 memVfs; /* VFS-implemented memory database */
/**************************************************************************
** The following block contains those class members that change during
** routine operation. Class members not in this block are either fixed
** when the pager is first created or else only change when there is a
** significant mode change (such as changing the page_size, locking_mode,
** or the journal_mode). From another view, these class members describe
** the "state" of the pager, while other class members describe the
** "configuration" of the pager.
*/
u8 eState; /* Pager state (OPEN, READER, WRITER_LOCKED..) */
u8 eLock; /* Current lock held on database file */
u8 changeCountDone; /* Set after incrementing the change-counter */
u8 setSuper; /* Super-jrnl name is written into jrnl */
u8 doNotSpill; /* Do not spill the cache when non-zero */
u8 subjInMemory; /* True to use in-memory sub-journals */
u8 bUseFetch; /* True to use xFetch() */
u8 hasHeldSharedLock; /* True if a shared lock has ever been held */
Pgno dbSize; /* Number of pages in the database */
Pgno dbOrigSize; /* dbSize before the current transaction */
Pgno dbFileSize; /* Number of pages in the database file */
Pgno dbHintSize; /* Value passed to FCNTL_SIZE_HINT call */
int errCode; /* One of several kinds of errors */
int nRec; /* Pages journalled since last j-header written */
u32 cksumInit; /* Quasi-random value added to every checksum */
u32 nSubRec; /* Number of records written to sub-journal */
Bitvec *pInJournal; /* One bit for each page in the database file */
sqlite3_file *fd; /* File descriptor for database */
sqlite3_file *jfd; /* File descriptor for main journal */
sqlite3_file *sjfd; /* File descriptor for sub-journal */
i64 journalOff; /* Current write offset in the journal file */
i64 journalHdr; /* Byte offset to previous journal header */
sqlite3_backup *pBackup; /* Pointer to list of ongoing backup processes */
PagerSavepoint *aSavepoint; /* Array of active savepoints */
int nSavepoint; /* Number of elements in aSavepoint[] */
u32 iDataVersion; /* Changes whenever database content changes */
char dbFileVers[16]; /* Changes whenever database file changes */
int nMmapOut; /* Number of mmap pages currently outstanding */
sqlite3_int64 szMmap; /* Desired maximum mmap size */
PgHdr *pMmapFreelist; /* List of free mmap page headers (pDirty) */
/*
** End of the routinely-changing class members
***************************************************************************/
u16 nExtra; /* Add this many bytes to each in-memory page */
i16 nReserve; /* Number of unused bytes at end of each page */
u32 vfsFlags; /* Flags for sqlite3_vfs.xOpen() */
u32 sectorSize; /* Assumed sector size during rollback */
Pgno mxPgno; /* Maximum allowed size of the database */
Pgno lckPgno; /* Page number for the locking page */
i64 pageSize; /* Number of bytes in a page */
i64 journalSizeLimit; /* Size limit for persistent journal files */
char *zFilename; /* Name of the database file */
char *zJournal; /* Name of the journal file */
int (*xBusyHandler)(void*); /* Function to call when busy */
void *pBusyHandlerArg; /* Context argument for xBusyHandler */
u32 aStat[4]; /* Total cache hits, misses, writes, spills */
#ifdef SQLITE_TEST
int nRead; /* Database pages read */
#endif
void (*xReiniter)(DbPage*); /* Call this routine when reloading pages */
int (*xGet)(Pager*,Pgno,DbPage**,int); /* Routine to fetch a patch */
char *pTmpSpace; /* Pager.pageSize bytes of space for tmp use */
PCache *pPCache; /* Pointer to page cache object */
#ifndef SQLITE_OMIT_WAL
Wal *pWal; /* Write-ahead log used by "journal_mode=wal" */
char *zWal; /* File name for write-ahead log */
#endif
};
/*
** Indexes for use with Pager.aStat[]. The Pager.aStat[] array contains
** the values accessed by passing SQLITE_DBSTATUS_CACHE_HIT, CACHE_MISS
** or CACHE_WRITE to sqlite3_db_status().
*/
#define PAGER_STAT_HIT 0
#define PAGER_STAT_MISS 1
#define PAGER_STAT_WRITE 2
#define PAGER_STAT_SPILL 3
/*
** The following global variables hold counters used for
** testing purposes only. These variables do not exist in
** a non-testing build. These variables are not thread-safe.
*/
#ifdef SQLITE_TEST
int sqlite3_pager_readdb_count = 0; /* Number of full pages read from DB */
int sqlite3_pager_writedb_count = 0; /* Number of full pages written to DB */
int sqlite3_pager_writej_count = 0; /* Number of pages written to journal */
# define PAGER_INCR(v) v++
#else
# define PAGER_INCR(v)
#endif
/*
** Journal files begin with the following magic string. The data
** was obtained from /dev/random. It is used only as a sanity check.
**
** Since version 2.8.0, the journal format contains additional sanity
** checking information. If the power fails while the journal is being
** written, semi-random garbage data might appear in the journal
** file after power is restored. If an attempt is then made
** to roll the journal back, the database could be corrupted. The additional
** sanity checking data is an attempt to discover the garbage in the
** journal and ignore it.
**
** The sanity checking information for the new journal format consists
** of a 32-bit checksum on each page of data. The checksum covers both
** the page number and the pPager->pageSize bytes of data for the page.
** This cksum is initialized to a 32-bit random value that appears in the
** journal file right after the header. The random initializer is important,
** because garbage data that appears at the end of a journal is likely
** data that was once in other files that have now been deleted. If the
** garbage data came from an obsolete journal file, the checksums might
** be correct. But by initializing the checksum to random value which
** is different for every journal, we minimize that risk.
*/
static const unsigned char aJournalMagic[] = {
0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd7,
};
/*
** The size of the of each page record in the journal is given by
** the following macro.
*/
#define JOURNAL_PG_SZ(pPager) ((pPager->pageSize) + 8)
/*
** The journal header size for this pager. This is usually the same
** size as a single disk sector. See also setSectorSize().
*/
#define JOURNAL_HDR_SZ(pPager) (pPager->sectorSize)
/*
** The macro MEMDB is true if we are dealing with an in-memory database.
** We do this as a macro so that if the SQLITE_OMIT_MEMORYDB macro is set,
** the value of MEMDB will be a constant and the compiler will optimize
** out code that would never execute.
*/
#ifdef SQLITE_OMIT_MEMORYDB
# define MEMDB 0
#else
# define MEMDB pPager->memDb
#endif
/*
** The macro USEFETCH is true if we are allowed to use the xFetch and xUnfetch
** interfaces to access the database using memory-mapped I/O.
*/
#if SQLITE_MAX_MMAP_SIZE>0
# define USEFETCH(x) ((x)->bUseFetch)
#else
# define USEFETCH(x) 0
#endif
/*
** The argument to this macro is a file descriptor (type sqlite3_file*).
** Return 0 if it is not open, or non-zero (but not 1) if it is.
**
** This is so that expressions can be written as:
**
** if( isOpen(pPager->jfd) ){ ...
**
** instead of
**
** if( pPager->jfd->pMethods ){ ...
*/
#define isOpen(pFd) ((pFd)->pMethods!=0)
#ifdef SQLITE_DIRECT_OVERFLOW_READ
/*
** Return true if page pgno can be read directly from the database file
** by the b-tree layer. This is the case if:
**
** (1) the database file is open
** (2) the VFS for the database is able to do unaligned sub-page reads
** (3) there are no dirty pages in the cache, and
** (4) the desired page is not currently in the wal file.
*/
int sqlite3PagerDirectReadOk(Pager *pPager, Pgno pgno){
assert( pPager!=0 );
assert( pPager->fd!=0 );
if( pPager->fd->pMethods==0 ) return 0; /* Case (1) */
if( sqlite3PCacheIsDirty(pPager->pPCache) ) return 0; /* Failed (3) */
#ifndef SQLITE_OMIT_WAL
if( pPager->pWal ){
u32 iRead = 0;
(void)sqlite3WalFindFrame(pPager->pWal, pgno, &iRead);
return iRead==0; /* Condition (4) */
}
#endif
assert( pPager->fd->pMethods->xDeviceCharacteristics!=0 );
if( (pPager->fd->pMethods->xDeviceCharacteristics(pPager->fd)
& SQLITE_IOCAP_SUBPAGE_READ)==0 ){
return 0; /* Case (2) */
}
return 1;
}
#endif
#ifndef SQLITE_OMIT_WAL
# define pagerUseWal(x) ((x)->pWal!=0)
#else
# define pagerUseWal(x) 0
# define pagerRollbackWal(x) 0
# define pagerWalFrames(v,w,x,y) 0
# define pagerOpenWalIfPresent(z) SQLITE_OK
# define pagerBeginReadTransaction(z) SQLITE_OK
#endif
#ifndef NDEBUG
/*
** Usage:
**
** assert( assert_pager_state(pPager) );
**
** This function runs many asserts to try to find inconsistencies in
** the internal state of the Pager object.
*/
static int assert_pager_state(Pager *p){
Pager *pPager = p;
/* State must be valid. */
assert( p->eState==PAGER_OPEN
|| p->eState==PAGER_READER
|| p->eState==PAGER_WRITER_LOCKED
|| p->eState==PAGER_WRITER_CACHEMOD
|| p->eState==PAGER_WRITER_DBMOD
|| p->eState==PAGER_WRITER_FINISHED
|| p->eState==PAGER_ERROR
);
/* Regardless of the current state, a temp-file connection always behaves
** as if it has an exclusive lock on the database file. It never updates
** the change-counter field, so the changeCountDone flag is always set.
*/
assert( p->tempFile==0 || p->eLock==EXCLUSIVE_LOCK );
assert( p->tempFile==0 || pPager->changeCountDone );
/* If the useJournal flag is clear, the journal-mode must be "OFF".
** And if the journal-mode is "OFF", the journal file must not be open.
*/
assert( p->journalMode==PAGER_JOURNALMODE_OFF || p->useJournal );
assert( p->journalMode!=PAGER_JOURNALMODE_OFF || !isOpen(p->jfd) );
/* Check that MEMDB implies noSync. And an in-memory journal. Since
** this means an in-memory pager performs no IO at all, it cannot encounter
** either SQLITE_IOERR or SQLITE_FULL during rollback or while finalizing
** a journal file. (although the in-memory journal implementation may
** return SQLITE_IOERR_NOMEM while the journal file is being written). It
** is therefore not possible for an in-memory pager to enter the ERROR
** state.
*/
if( MEMDB ){
assert( !isOpen(p->fd) );
assert( p->noSync );
assert( p->journalMode==PAGER_JOURNALMODE_OFF
|| p->journalMode==PAGER_JOURNALMODE_MEMORY
);
assert( p->eState!=PAGER_ERROR && p->eState!=PAGER_OPEN );
assert( pagerUseWal(p)==0 );
}
/* If changeCountDone is set, a RESERVED lock or greater must be held
** on the file.
*/
assert( pPager->changeCountDone==0 || pPager->eLock>=RESERVED_LOCK );
assert( p->eLock!=PENDING_LOCK );
switch( p->eState ){
case PAGER_OPEN:
assert( !MEMDB );
assert( pPager->errCode==SQLITE_OK );
assert( sqlite3PcacheRefCount(pPager->pPCache)==0 || pPager->tempFile );
break;
case PAGER_READER:
assert( pPager->errCode==SQLITE_OK );
assert( p->eLock!=UNKNOWN_LOCK );
assert( p->eLock>=SHARED_LOCK );
break;
case PAGER_WRITER_LOCKED:
assert( p->eLock!=UNKNOWN_LOCK );
assert( pPager->errCode==SQLITE_OK );
if( !pagerUseWal(pPager) ){
assert( p->eLock>=RESERVED_LOCK );
}
assert( pPager->dbSize==pPager->dbOrigSize );
assert( pPager->dbOrigSize==pPager->dbFileSize );
assert( pPager->dbOrigSize==pPager->dbHintSize );
assert( pPager->setSuper==0 );
break;
case PAGER_WRITER_CACHEMOD:
assert( p->eLock!=UNKNOWN_LOCK );
assert( pPager->errCode==SQLITE_OK );
if( !pagerUseWal(pPager) ){
/* It is possible that if journal_mode=wal here that neither the
** journal file nor the WAL file are open. This happens during
** a rollback transaction that switches from journal_mode=off
** to journal_mode=wal.
*/
assert( p->eLock>=RESERVED_LOCK );
assert( isOpen(p->jfd)
|| p->journalMode==PAGER_JOURNALMODE_OFF
|| p->journalMode==PAGER_JOURNALMODE_WAL
);
}
assert( pPager->dbOrigSize==pPager->dbFileSize );
assert( pPager->dbOrigSize==pPager->dbHintSize );
break;
case PAGER_WRITER_DBMOD:
assert( p->eLock==EXCLUSIVE_LOCK );
assert( pPager->errCode==SQLITE_OK );
assert( !pagerUseWal(pPager) );
assert( p->eLock>=EXCLUSIVE_LOCK );
assert( isOpen(p->jfd)
|| p->journalMode==PAGER_JOURNALMODE_OFF
|| p->journalMode==PAGER_JOURNALMODE_WAL
|| (sqlite3OsDeviceCharacteristics(p->fd)&SQLITE_IOCAP_BATCH_ATOMIC)
);
assert( pPager->dbOrigSize<=pPager->dbHintSize );
break;
case PAGER_WRITER_FINISHED:
assert( p->eLock==EXCLUSIVE_LOCK );
assert( pPager->errCode==SQLITE_OK );
assert( !pagerUseWal(pPager) );
assert( isOpen(p->jfd)
|| p->journalMode==PAGER_JOURNALMODE_OFF
|| p->journalMode==PAGER_JOURNALMODE_WAL
|| (sqlite3OsDeviceCharacteristics(p->fd)&SQLITE_IOCAP_BATCH_ATOMIC)
);
break;
case PAGER_ERROR:
/* There must be at least one outstanding reference to the pager if
** in ERROR state. Otherwise the pager should have already dropped
** back to OPEN state.
*/
assert( pPager->errCode!=SQLITE_OK );
assert( sqlite3PcacheRefCount(pPager->pPCache)>0 || pPager->tempFile );
break;
}
return 1;
}
#endif /* ifndef NDEBUG */
#ifdef SQLITE_DEBUG
/*
** Return a pointer to a human readable string in a static buffer
** containing the state of the Pager object passed as an argument. This
** is intended to be used within debuggers. For example, as an alternative
** to "print *pPager" in gdb:
**
** (gdb) printf "%s", print_pager_state(pPager)
**
** This routine has external linkage in order to suppress compiler warnings
** about an unused function. It is enclosed within SQLITE_DEBUG and so does
** not appear in normal builds.
*/
char *print_pager_state(Pager *p){
static char zRet[1024];
sqlite3_snprintf(1024, zRet,
"Filename: %s\n"
"State: %s errCode=%d\n"
"Lock: %s\n"
"Locking mode: locking_mode=%s\n"
"Journal mode: journal_mode=%s\n"
"Backing store: tempFile=%d memDb=%d useJournal=%d\n"
"Journal: journalOff=%lld journalHdr=%lld\n"
"Size: dbsize=%d dbOrigSize=%d dbFileSize=%d\n"
, p->zFilename
, p->eState==PAGER_OPEN ? "OPEN" :
p->eState==PAGER_READER ? "READER" :
p->eState==PAGER_WRITER_LOCKED ? "WRITER_LOCKED" :
p->eState==PAGER_WRITER_CACHEMOD ? "WRITER_CACHEMOD" :
p->eState==PAGER_WRITER_DBMOD ? "WRITER_DBMOD" :
p->eState==PAGER_WRITER_FINISHED ? "WRITER_FINISHED" :
p->eState==PAGER_ERROR ? "ERROR" : "?error?"
, (int)p->errCode
, p->eLock==NO_LOCK ? "NO_LOCK" :
p->eLock==RESERVED_LOCK ? "RESERVED" :
p->eLock==EXCLUSIVE_LOCK ? "EXCLUSIVE" :
p->eLock==SHARED_LOCK ? "SHARED" :
p->eLock==UNKNOWN_LOCK ? "UNKNOWN" : "?error?"
, p->exclusiveMode ? "exclusive" : "normal"
, p->journalMode==PAGER_JOURNALMODE_MEMORY ? "memory" :
p->journalMode==PAGER_JOURNALMODE_OFF ? "off" :
p->journalMode==PAGER_JOURNALMODE_DELETE ? "delete" :
p->journalMode==PAGER_JOURNALMODE_PERSIST ? "persist" :
p->journalMode==PAGER_JOURNALMODE_TRUNCATE ? "truncate" :
p->journalMode==PAGER_JOURNALMODE_WAL ? "wal" : "?error?"
, (int)p->tempFile, (int)p->memDb, (int)p->useJournal
, p->journalOff, p->journalHdr
, (int)p->dbSize, (int)p->dbOrigSize, (int)p->dbFileSize
);
return zRet;
}
#endif
/* Forward references to the various page getters */
static int getPageNormal(Pager*,Pgno,DbPage**,int);
static int getPageError(Pager*,Pgno,DbPage**,int);
#if SQLITE_MAX_MMAP_SIZE>0
static int getPageMMap(Pager*,Pgno,DbPage**,int);
#endif
/*
** Set the Pager.xGet method for the appropriate routine used to fetch
** content from the pager.
*/
static void setGetterMethod(Pager *pPager){
if( pPager->errCode ){
pPager->xGet = getPageError;
#if SQLITE_MAX_MMAP_SIZE>0
}else if( USEFETCH(pPager) ){
pPager->xGet = getPageMMap;
#endif /* SQLITE_MAX_MMAP_SIZE>0 */
}else{
pPager->xGet = getPageNormal;
}
}
/*
** Return true if it is necessary to write page *pPg into the sub-journal.
** A page needs to be written into the sub-journal if there exists one
** or more open savepoints for which:
**
** * The page-number is less than or equal to PagerSavepoint.nOrig, and
** * The bit corresponding to the page-number is not set in
** PagerSavepoint.pInSavepoint.
*/
static int subjRequiresPage(PgHdr *pPg){
Pager *pPager = pPg->pPager;
PagerSavepoint *p;
Pgno pgno = pPg->pgno;
int i;
for(i=0; i<pPager->nSavepoint; i++){
p = &pPager->aSavepoint[i];
if( p->nOrig>=pgno && 0==sqlite3BitvecTestNotNull(p->pInSavepoint, pgno) ){
for(i=i+1; i<pPager->nSavepoint; i++){
pPager->aSavepoint[i].bTruncateOnRelease = 0;
}
return 1;
}
}
return 0;
}
#ifdef SQLITE_DEBUG
/*
** Return true if the page is already in the journal file.
*/
static int pageInJournal(Pager *pPager, PgHdr *pPg){
return sqlite3BitvecTest(pPager->pInJournal, pPg->pgno);
}
#endif
/*
** Read a 32-bit integer from the given file descriptor. Store the integer
** that is read in *pRes. Return SQLITE_OK if everything worked, or an
** error code is something goes wrong.
**
** All values are stored on disk as big-endian.
*/
static int read32bits(sqlite3_file *fd, i64 offset, u32 *pRes){
unsigned char ac[4];
int rc = sqlite3OsRead(fd, ac, sizeof(ac), offset);
if( rc==SQLITE_OK ){
*pRes = sqlite3Get4byte(ac);
}
return rc;
}
/*
** Write a 32-bit integer into a string buffer in big-endian byte order.
*/
#define put32bits(A,B) sqlite3Put4byte((u8*)A,B)
/*
** Write a 32-bit integer into the given file descriptor. Return SQLITE_OK
** on success or an error code is something goes wrong.
*/
static int write32bits(sqlite3_file *fd, i64 offset, u32 val){
char ac[4];
put32bits(ac, val);
return sqlite3OsWrite(fd, ac, 4, offset);
}
/*
** Unlock the database file to level eLock, which must be either NO_LOCK
** or SHARED_LOCK. Regardless of whether or not the call to xUnlock()
** succeeds, set the Pager.eLock variable to match the (attempted) new lock.
**
** Except, if Pager.eLock is set to UNKNOWN_LOCK when this function is
** called, do not modify it. See the comment above the #define of
** UNKNOWN_LOCK for an explanation of this.
*/
static int pagerUnlockDb(Pager *pPager, int eLock){
int rc = SQLITE_OK;
assert( !pPager->exclusiveMode || pPager->eLock==eLock );
assert( eLock==NO_LOCK || eLock==SHARED_LOCK );
assert( eLock!=NO_LOCK || pagerUseWal(pPager)==0 );
if( isOpen(pPager->fd) ){
assert( pPager->eLock>=eLock );
rc = pPager->noLock ? SQLITE_OK : sqlite3OsUnlock(pPager->fd, eLock);
if( pPager->eLock!=UNKNOWN_LOCK ){
pPager->eLock = (u8)eLock;
}
IOTRACE(("UNLOCK %p %d\n", pPager, eLock))
}
pPager->changeCountDone = pPager->tempFile; /* ticket fb3b3024ea238d5c */
return rc;
}
/*
** Lock the database file to level eLock, which must be either SHARED_LOCK,
** RESERVED_LOCK or EXCLUSIVE_LOCK. If the caller is successful, set the
** Pager.eLock variable to the new locking state.
**
** Except, if Pager.eLock is set to UNKNOWN_LOCK when this function is
** called, do not modify it unless the new locking state is EXCLUSIVE_LOCK.
** See the comment above the #define of UNKNOWN_LOCK for an explanation
** of this.
*/
static int pagerLockDb(Pager *pPager, int eLock){
int rc = SQLITE_OK;
assert( eLock==SHARED_LOCK || eLock==RESERVED_LOCK || eLock==EXCLUSIVE_LOCK );
if( pPager->eLock<eLock || pPager->eLock==UNKNOWN_LOCK ){
rc = pPager->noLock ? SQLITE_OK : sqlite3OsLock(pPager->fd, eLock);
if( rc==SQLITE_OK && (pPager->eLock!=UNKNOWN_LOCK||eLock==EXCLUSIVE_LOCK) ){
pPager->eLock = (u8)eLock;
IOTRACE(("LOCK %p %d\n", pPager, eLock))
}
}
return rc;
}
/*
** This function determines whether or not the atomic-write or
** atomic-batch-write optimizations can be used with this pager. The
** atomic-write optimization can be used if:
**
** (a) the value returned by OsDeviceCharacteristics() indicates that
** a database page may be written atomically, and
** (b) the value returned by OsSectorSize() is less than or equal
** to the page size.
**
** If it can be used, then the value returned is the size of the journal
** file when it contains rollback data for exactly one page.
**
** The atomic-batch-write optimization can be used if OsDeviceCharacteristics()
** returns a value with the SQLITE_IOCAP_BATCH_ATOMIC bit set. -1 is
** returned in this case.
**
** If neither optimization can be used, 0 is returned.
*/
static int jrnlBufferSize(Pager *pPager){
assert( !MEMDB );
#if defined(SQLITE_ENABLE_ATOMIC_WRITE) \
|| defined(SQLITE_ENABLE_BATCH_ATOMIC_WRITE)
int dc; /* Device characteristics */
assert( isOpen(pPager->fd) );
dc = sqlite3OsDeviceCharacteristics(pPager->fd);
#else
UNUSED_PARAMETER(pPager);
#endif
#ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE
if( pPager->dbSize>0 && (dc&SQLITE_IOCAP_BATCH_ATOMIC) ){
return -1;
}
#endif
#ifdef SQLITE_ENABLE_ATOMIC_WRITE
{
int nSector = pPager->sectorSize;
int szPage = pPager->pageSize;
assert(SQLITE_IOCAP_ATOMIC512==(512>>8));
assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8));
if( 0==(dc&(SQLITE_IOCAP_ATOMIC|(szPage>>8)) || nSector>szPage) ){
return 0;
}
}
return JOURNAL_HDR_SZ(pPager) + JOURNAL_PG_SZ(pPager);
#endif
return 0;
}
/*
** If SQLITE_CHECK_PAGES is defined then we do some sanity checking
** on the cache using a hash function. This is used for testing
** and debugging only.
*/
#ifdef SQLITE_CHECK_PAGES
/*
** Return a 32-bit hash of the page data for pPage.
*/
static u32 pager_datahash(int nByte, unsigned char *pData){
u32 hash = 0;
int i;
for(i=0; i<nByte; i++){
hash = (hash*1039) + pData[i];
}
return hash;
}
static u32 pager_pagehash(PgHdr *pPage){
return pager_datahash(pPage->pPager->pageSize, (unsigned char *)pPage->pData);
}
static void pager_set_pagehash(PgHdr *pPage){
pPage->pageHash = pager_pagehash(pPage);
}
/*
** The CHECK_PAGE macro takes a PgHdr* as an argument. If SQLITE_CHECK_PAGES
** is defined, and NDEBUG is not defined, an assert() statement checks
** that the page is either dirty or still matches the calculated page-hash.
*/
#define CHECK_PAGE(x) checkPage(x)
static void checkPage(PgHdr *pPg){
Pager *pPager = pPg->pPager;
assert( pPager->eState!=PAGER_ERROR );
assert( (pPg->flags&PGHDR_DIRTY) || pPg->pageHash==pager_pagehash(pPg) );
}
#else
#define pager_datahash(X,Y) 0
#define pager_pagehash(X) 0
#define pager_set_pagehash(X)
#define CHECK_PAGE(x)
#endif /* SQLITE_CHECK_PAGES */
/*
** When this is called the journal file for pager pPager must be open.
** This function attempts to read a super-journal file name from the
** end of the file and, if successful, copies it into memory supplied
** by the caller. See comments above writeSuperJournal() for the format
** used to store a super-journal file name at the end of a journal file.
**
** zSuper must point to a buffer of at least nSuper bytes allocated by
** the caller. This should be sqlite3_vfs.mxPathname+1 (to ensure there is
** enough space to write the super-journal name). If the super-journal
** name in the journal is longer than nSuper bytes (including a
** nul-terminator), then this is handled as if no super-journal name
** were present in the journal.
**
** If a super-journal file name is present at the end of the journal
** file, then it is copied into the buffer pointed to by zSuper. A
** nul-terminator byte is appended to the buffer following the
** super-journal file name.
**
** If it is determined that no super-journal file name is present
** zSuper[0] is set to 0 and SQLITE_OK returned.
**
** If an error occurs while reading from the journal file, an SQLite
** error code is returned.
*/
static int readSuperJournal(sqlite3_file *pJrnl, char *zSuper, u32 nSuper){
int rc; /* Return code */
u32 len; /* Length in bytes of super-journal name */
i64 szJ; /* Total size in bytes of journal file pJrnl */
u32 cksum; /* MJ checksum value read from journal */
u32 u; /* Unsigned loop counter */
unsigned char aMagic[8]; /* A buffer to hold the magic header */
zSuper[0] = '\0';
if( SQLITE_OK!=(rc = sqlite3OsFileSize(pJrnl, &szJ))
|| szJ<16
|| SQLITE_OK!=(rc = read32bits(pJrnl, szJ-16, &len))
|| len>=nSuper
|| len>szJ-16
|| len==0
|| SQLITE_OK!=(rc = read32bits(pJrnl, szJ-12, &cksum))
|| SQLITE_OK!=(rc = sqlite3OsRead(pJrnl, aMagic, 8, szJ-8))
|| memcmp(aMagic, aJournalMagic, 8)
|| SQLITE_OK!=(rc = sqlite3OsRead(pJrnl, zSuper, len, szJ-16-len))
){
return rc;
}
/* See if the checksum matches the super-journal name */
for(u=0; u<len; u++){
cksum -= zSuper[u];
}
if( cksum ){
/* If the checksum doesn't add up, then one or more of the disk sectors
** containing the super-journal filename is corrupted. This means
** definitely roll back, so just return SQLITE_OK and report a (nul)
** super-journal filename.
*/
len = 0;
}
zSuper[len] = '\0';
zSuper[len+1] = '\0';
return SQLITE_OK;
}
/*
** Return the offset of the sector boundary at or immediately
** following the value in pPager->journalOff, assuming a sector
** size of pPager->sectorSize bytes.
**
** i.e for a sector size of 512:
**
** Pager.journalOff Return value
** ---------------------------------------
** 0 0
** 512 512
** 100 512
** 2000 2048
**
*/
static i64 journalHdrOffset(Pager *pPager){
i64 offset = 0;
i64 c = pPager->journalOff;
if( c ){
offset = ((c-1)/JOURNAL_HDR_SZ(pPager) + 1) * JOURNAL_HDR_SZ(pPager);
}
assert( offset%JOURNAL_HDR_SZ(pPager)==0 );
assert( offset>=c );
assert( (offset-c)<JOURNAL_HDR_SZ(pPager) );
return offset;
}
/*
** The journal file must be open when this function is called.
**
** This function is a no-op if the journal file has not been written to
** within the current transaction (i.e. if Pager.journalOff==0).
**
** If doTruncate is non-zero or the Pager.journalSizeLimit variable is
** set to 0, then truncate the journal file to zero bytes in size. Otherwise,
** zero the 28-byte header at the start of the journal file. In either case,
** if the pager is not in no-sync mode, sync the journal file immediately
** after writing or truncating it.
**
** If Pager.journalSizeLimit is set to a positive, non-zero value, and
** following the truncation or zeroing described above the size of the
** journal file in bytes is larger than this value, then truncate the
** journal file to Pager.journalSizeLimit bytes. The journal file does
** not need to be synced following this operation.
**
** If an IO error occurs, abandon processing and return the IO error code.
** Otherwise, return SQLITE_OK.
*/
static int zeroJournalHdr(Pager *pPager, int doTruncate){
int rc = SQLITE_OK; /* Return code */
assert( isOpen(pPager->jfd) );
assert( !sqlite3JournalIsInMemory(pPager->jfd) );
if( pPager->journalOff ){
const i64 iLimit = pPager->journalSizeLimit; /* Local cache of jsl */
IOTRACE(("JZEROHDR %p\n", pPager))
if( doTruncate || iLimit==0 ){
rc = sqlite3OsTruncate(pPager->jfd, 0);
}else{
static const char zeroHdr[28] = {0};
rc = sqlite3OsWrite(pPager->jfd, zeroHdr, sizeof(zeroHdr), 0);
}
if( rc==SQLITE_OK && !pPager->noSync ){
rc = sqlite3OsSync(pPager->jfd, SQLITE_SYNC_DATAONLY|pPager->syncFlags);
}
/* At this point the transaction is committed but the write lock
** is still held on the file. If there is a size limit configured for
** the persistent journal and the journal file currently consumes more
** space than that limit allows for, truncate it now. There is no need
** to sync the file following this operation.
*/
if( rc==SQLITE_OK && iLimit>0 ){
i64 sz;
rc = sqlite3OsFileSize(pPager->jfd, &sz);
if( rc==SQLITE_OK && sz>iLimit ){
rc = sqlite3OsTruncate(pPager->jfd, iLimit);
}
}
}
return rc;
}
/*
** The journal file must be open when this routine is called. A journal
** header (JOURNAL_HDR_SZ bytes) is written into the journal file at the
** current location.
**
** The format for the journal header is as follows:
** - 8 bytes: Magic identifying journal format.
** - 4 bytes: Number of records in journal, or -1 no-sync mode is on.
** - 4 bytes: Random number used for page hash.
** - 4 bytes: Initial database page count.
** - 4 bytes: Sector size used by the process that wrote this journal.
** - 4 bytes: Database page size.
**
** Followed by (JOURNAL_HDR_SZ - 28) bytes of unused space.
*/
static int writeJournalHdr(Pager *pPager){
int rc = SQLITE_OK; /* Return code */
char *zHeader = pPager->pTmpSpace; /* Temporary space used to build header */
u32 nHeader = (u32)pPager->pageSize;/* Size of buffer pointed to by zHeader */
u32 nWrite; /* Bytes of header sector written */
int ii; /* Loop counter */
assert( isOpen(pPager->jfd) ); /* Journal file must be open. */
if( nHeader>JOURNAL_HDR_SZ(pPager) ){
nHeader = JOURNAL_HDR_SZ(pPager);
}
/* If there are active savepoints and any of them were created
** since the most recent journal header was written, update the
** PagerSavepoint.iHdrOffset fields now.
*/
for(ii=0; ii<pPager->nSavepoint; ii++){
if( pPager->aSavepoint[ii].iHdrOffset==0 ){
pPager->aSavepoint[ii].iHdrOffset = pPager->journalOff;
}
}
pPager->journalHdr = pPager->journalOff = journalHdrOffset(pPager);
/*
** Write the nRec Field - the number of page records that follow this
** journal header. Normally, zero is written to this value at this time.
** After the records are added to the journal (and the journal synced,
** if in full-sync mode), the zero is overwritten with the true number
** of records (see syncJournal()).
**
** A faster alternative is to write 0xFFFFFFFF to the nRec field. When
** reading the journal this value tells SQLite to assume that the
** rest of the journal file contains valid page records. This assumption
** is dangerous, as if a failure occurred whilst writing to the journal
** file it may contain some garbage data. There are two scenarios
** where this risk can be ignored:
**
** * When the pager is in no-sync mode. Corruption can follow a
** power failure in this case anyway.
**
** * When the SQLITE_IOCAP_SAFE_APPEND flag is set. This guarantees
** that garbage data is never appended to the journal file.
*/
assert( isOpen(pPager->fd) || pPager->noSync );
if( pPager->noSync || (pPager->journalMode==PAGER_JOURNALMODE_MEMORY)
|| (sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_SAFE_APPEND)
){
memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic));
put32bits(&zHeader[sizeof(aJournalMagic)], 0xffffffff);
}else{
memset(zHeader, 0, sizeof(aJournalMagic)+4);
}
/* The random check-hash initializer */
if( pPager->journalMode!=PAGER_JOURNALMODE_MEMORY ){
sqlite3_randomness(sizeof(pPager->cksumInit), &pPager->cksumInit);
}
#ifdef SQLITE_DEBUG
else{
/* The Pager.cksumInit variable is usually randomized above to protect
** against there being existing records in the journal file. This is
** dangerous, as following a crash they may be mistaken for records
** written by the current transaction and rolled back into the database
** file, causing corruption. The following assert statements verify
** that this is not required in "journal_mode=memory" mode, as in that
** case the journal file is always 0 bytes in size at this point.
** It is advantageous to avoid the sqlite3_randomness() call if possible
** as it takes the global PRNG mutex. */
i64 sz = 0;
sqlite3OsFileSize(pPager->jfd, &sz);
assert( sz==0 );
assert( pPager->journalOff==journalHdrOffset(pPager) );
assert( sqlite3JournalIsInMemory(pPager->jfd) );
}
#endif
put32bits(&zHeader[sizeof(aJournalMagic)+4], pPager->cksumInit);
/* The initial database size */
put32bits(&zHeader[sizeof(aJournalMagic)+8], pPager->dbOrigSize);
/* The assumed sector size for this process */
put32bits(&zHeader[sizeof(aJournalMagic)+12], pPager->sectorSize);
/* The page size */
put32bits(&zHeader[sizeof(aJournalMagic)+16], pPager->pageSize);
/* Initializing the tail of the buffer is not necessary. Everything
** works find if the following memset() is omitted. But initializing
** the memory prevents valgrind from complaining, so we are willing to
** take the performance hit.
*/
memset(&zHeader[sizeof(aJournalMagic)+20], 0,
nHeader-(sizeof(aJournalMagic)+20));
/* In theory, it is only necessary to write the 28 bytes that the
** journal header consumes to the journal file here. Then increment the
** Pager.journalOff variable by JOURNAL_HDR_SZ so that the next
** record is written to the following sector (leaving a gap in the file
** that will be implicitly filled in by the OS).
**
** However it has been discovered that on some systems this pattern can
** be significantly slower than contiguously writing data to the file,
** even if that means explicitly writing data to the block of
** (JOURNAL_HDR_SZ - 28) bytes that will not be used. So that is what
** is done.
**
** The loop is required here in case the sector-size is larger than the
** database page size. Since the zHeader buffer is only Pager.pageSize
** bytes in size, more than one call to sqlite3OsWrite() may be required
** to populate the entire journal header sector.
*/
for(nWrite=0; rc==SQLITE_OK&&nWrite<JOURNAL_HDR_SZ(pPager); nWrite+=nHeader){
IOTRACE(("JHDR %p %lld %d\n", pPager, pPager->journalHdr, nHeader))
rc = sqlite3OsWrite(pPager->jfd, zHeader, nHeader, pPager->journalOff);
assert( pPager->journalHdr <= pPager->journalOff );
pPager->journalOff += nHeader;
}
return rc;
}
/*
** The journal file must be open when this is called. A journal header file
** (JOURNAL_HDR_SZ bytes) is read from the current location in the journal
** file. The current location in the journal file is given by
** pPager->journalOff. See comments above function writeJournalHdr() for
** a description of the journal header format.
**
** If the header is read successfully, *pNRec is set to the number of
** page records following this header and *pDbSize is set to the size of the
** database before the transaction began, in pages. Also, pPager->cksumInit
** is set to the value read from the journal header. SQLITE_OK is returned
** in this case.
**
** If the journal header file appears to be corrupted, SQLITE_DONE is
** returned and *pNRec and *PDbSize are undefined. If JOURNAL_HDR_SZ bytes
** cannot be read from the journal file an error code is returned.
*/
static int readJournalHdr(
Pager *pPager, /* Pager object */
int isHot,
i64 journalSize, /* Size of the open journal file in bytes */
u32 *pNRec, /* OUT: Value read from the nRec field */
u32 *pDbSize /* OUT: Value of original database size field */
){
int rc; /* Return code */
unsigned char aMagic[8]; /* A buffer to hold the magic header */
i64 iHdrOff; /* Offset of journal header being read */
assert( isOpen(pPager->jfd) ); /* Journal file must be open. */
/* Advance Pager.journalOff to the start of the next sector. If the
** journal file is too small for there to be a header stored at this
** point, return SQLITE_DONE.
*/
pPager->journalOff = journalHdrOffset(pPager);
if( pPager->journalOff+JOURNAL_HDR_SZ(pPager) > journalSize ){
return SQLITE_DONE;
}
iHdrOff = pPager->journalOff;
/* Read in the first 8 bytes of the journal header. If they do not match
** the magic string found at the start of each journal header, return
** SQLITE_DONE. If an IO error occurs, return an error code. Otherwise,
** proceed.
*/
if( isHot || iHdrOff!=pPager->journalHdr ){
rc = sqlite3OsRead(pPager->jfd, aMagic, sizeof(aMagic), iHdrOff);
if( rc ){
return rc;
}
if( memcmp(aMagic, aJournalMagic, sizeof(aMagic))!=0 ){
return SQLITE_DONE;
}
}
/* Read the first three 32-bit fields of the journal header: The nRec
** field, the checksum-initializer and the database size at the start
** of the transaction. Return an error code if anything goes wrong.
*/
if( SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+8, pNRec))
|| SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+12, &pPager->cksumInit))
|| SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+16, pDbSize))
){
return rc;
}
if( pPager->journalOff==0 ){
u32 iPageSize; /* Page-size field of journal header */
u32 iSectorSize; /* Sector-size field of journal header */
/* Read the page-size and sector-size journal header fields. */
if( SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+20, &iSectorSize))
|| SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+24, &iPageSize))
){
return rc;
}
/* Versions of SQLite prior to 3.5.8 set the page-size field of the
** journal header to zero. In this case, assume that the Pager.pageSize
** variable is already set to the correct page size.
*/
if( iPageSize==0 ){
iPageSize = pPager->pageSize;
}
/* Check that the values read from the page-size and sector-size fields
** are within range. To be 'in range', both values need to be a power
** of two greater than or equal to 512 or 32, and not greater than their
** respective compile time maximum limits.
*/
if( iPageSize<512 || iSectorSize<32
|| iPageSize>SQLITE_MAX_PAGE_SIZE || iSectorSize>MAX_SECTOR_SIZE
|| ((iPageSize-1)&iPageSize)!=0 || ((iSectorSize-1)&iSectorSize)!=0
){
/* If the either the page-size or sector-size in the journal-header is
** invalid, then the process that wrote the journal-header must have
** crashed before the header was synced. In this case stop reading
** the journal file here.
*/
return SQLITE_DONE;
}
/* Update the page-size to match the value read from the journal.
** Use a testcase() macro to make sure that malloc failure within
** PagerSetPagesize() is tested.
*/
rc = sqlite3PagerSetPagesize(pPager, &iPageSize, -1);
testcase( rc!=SQLITE_OK );
/* Update the assumed sector-size to match the value used by
** the process that created this journal. If this journal was
** created by a process other than this one, then this routine
** is being called from within pager_playback(). The local value
** of Pager.sectorSize is restored at the end of that routine.
*/
pPager->sectorSize = iSectorSize;
}
pPager->journalOff += JOURNAL_HDR_SZ(pPager);
return rc;
}
/*
** Write the supplied super-journal name into the journal file for pager
** pPager at the current location. The super-journal name must be the last
** thing written to a journal file. If the pager is in full-sync mode, the
** journal file descriptor is advanced to the next sector boundary before
** anything is written. The format is:
**
** + 4 bytes: PAGER_SJ_PGNO.
** + N bytes: super-journal filename in utf-8.
** + 4 bytes: N (length of super-journal name in bytes, no nul-terminator).
** + 4 bytes: super-journal name checksum.
** + 8 bytes: aJournalMagic[].
**
** The super-journal page checksum is the sum of the bytes in the super-journal
** name, where each byte is interpreted as a signed 8-bit integer.
**
** If zSuper is a NULL pointer (occurs for a single database transaction),
** this call is a no-op.
*/
static int writeSuperJournal(Pager *pPager, const char *zSuper){
int rc; /* Return code */
int nSuper; /* Length of string zSuper */
i64 iHdrOff; /* Offset of header in journal file */
i64 jrnlSize; /* Size of journal file on disk */
u32 cksum = 0; /* Checksum of string zSuper */
assert( pPager->setSuper==0 );
assert( !pagerUseWal(pPager) );
if( !zSuper
|| pPager->journalMode==PAGER_JOURNALMODE_MEMORY
|| !isOpen(pPager->jfd)
){
return SQLITE_OK;
}
pPager->setSuper = 1;
assert( pPager->journalHdr <= pPager->journalOff );
/* Calculate the length in bytes and the checksum of zSuper */
for(nSuper=0; zSuper[nSuper]; nSuper++){
cksum += zSuper[nSuper];
}
/* If in full-sync mode, advance to the next disk sector before writing
** the super-journal name. This is in case the previous page written to
** the journal has already been synced.
*/
if( pPager->fullSync ){
pPager->journalOff = journalHdrOffset(pPager);
}
iHdrOff = pPager->journalOff;
/* Write the super-journal data to the end of the journal file. If
** an error occurs, return the error code to the caller.
*/
if( (0 != (rc = write32bits(pPager->jfd, iHdrOff, PAGER_SJ_PGNO(pPager))))
|| (0 != (rc = sqlite3OsWrite(pPager->jfd, zSuper, nSuper, iHdrOff+4)))
|| (0 != (rc = write32bits(pPager->jfd, iHdrOff+4+nSuper, nSuper)))
|| (0 != (rc = write32bits(pPager->jfd, iHdrOff+4+nSuper+4, cksum)))
|| (0 != (rc = sqlite3OsWrite(pPager->jfd, aJournalMagic, 8,
iHdrOff+4+nSuper+8)))
){
return rc;
}
pPager->journalOff += (nSuper+20);
/* If the pager is in persistent-journal mode, then the physical
** journal-file may extend past the end of the super-journal name
** and 8 bytes of magic data just written to the file. This is
** dangerous because the code to rollback a hot-journal file
** will not be able to find the super-journal name to determine
** whether or not the journal is hot.
**
** Easiest thing to do in this scenario is to truncate the journal
** file to the required size.
*/
if( SQLITE_OK==(rc = sqlite3OsFileSize(pPager->jfd, &jrnlSize))
&& jrnlSize>pPager->journalOff
){
rc = sqlite3OsTruncate(pPager->jfd, pPager->journalOff);
}
return rc;
}
/*
** Discard the entire contents of the in-memory page-cache.
*/
static void pager_reset(Pager *pPager){
pPager->iDataVersion++;
sqlite3BackupRestart(pPager->pBackup);
sqlite3PcacheClear(pPager->pPCache);
}
/*
** Return the pPager->iDataVersion value
*/
u32 sqlite3PagerDataVersion(Pager *pPager){
return pPager->iDataVersion;
}
/*
** Free all structures in the Pager.aSavepoint[] array and set both
** Pager.aSavepoint and Pager.nSavepoint to zero. Close the sub-journal
** if it is open and the pager is not in exclusive mode.
*/
static void releaseAllSavepoints(Pager *pPager){
int ii; /* Iterator for looping through Pager.aSavepoint */
for(ii=0; ii<pPager->nSavepoint; ii++){
sqlite3BitvecDestroy(pPager->aSavepoint[ii].pInSavepoint);
}
if( !pPager->exclusiveMode || sqlite3JournalIsInMemory(pPager->sjfd) ){
sqlite3OsClose(pPager->sjfd);
}
sqlite3_free(pPager->aSavepoint);
pPager->aSavepoint = 0;
pPager->nSavepoint = 0;
pPager->nSubRec = 0;
}
/*
** Set the bit number pgno in the PagerSavepoint.pInSavepoint
** bitvecs of all open savepoints. Return SQLITE_OK if successful
** or SQLITE_NOMEM if a malloc failure occurs.
*/
static int addToSavepointBitvecs(Pager *pPager, Pgno pgno){
int ii; /* Loop counter */
int rc = SQLITE_OK; /* Result code */
for(ii=0; ii<pPager->nSavepoint; ii++){
PagerSavepoint *p = &pPager->aSavepoint[ii];
if( pgno<=p->nOrig ){
rc |= sqlite3BitvecSet(p->pInSavepoint, pgno);
testcase( rc==SQLITE_NOMEM );
assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
}
}
return rc;
}
/*
** This function is a no-op if the pager is in exclusive mode and not
** in the ERROR state. Otherwise, it switches the pager to PAGER_OPEN
** state.
**
** If the pager is not in exclusive-access mode, the database file is
** completely unlocked. If the file is unlocked and the file-system does
** not exhibit the UNDELETABLE_WHEN_OPEN property, the journal file is
** closed (if it is open).
**
** If the pager is in ERROR state when this function is called, the
** contents of the pager cache are discarded before switching back to
** the OPEN state. Regardless of whether the pager is in exclusive-mode
** or not, any journal file left in the file-system will be treated
** as a hot-journal and rolled back the next time a read-transaction
** is opened (by this or by any other connection).
*/
static void pager_unlock(Pager *pPager){
assert( pPager->eState==PAGER_READER
|| pPager->eState==PAGER_OPEN
|| pPager->eState==PAGER_ERROR
);
sqlite3BitvecDestroy(pPager->pInJournal);
pPager->pInJournal = 0;
releaseAllSavepoints(pPager);
if( pagerUseWal(pPager) ){
assert( !isOpen(pPager->jfd) );
sqlite3WalEndReadTransaction(pPager->pWal);
pPager->eState = PAGER_OPEN;
}else if( !pPager->exclusiveMode ){
int rc; /* Error code returned by pagerUnlockDb() */
int iDc = isOpen(pPager->fd)?sqlite3OsDeviceCharacteristics(pPager->fd):0;
/* If the operating system support deletion of open files, then
** close the journal file when dropping the database lock. Otherwise
** another connection with journal_mode=delete might delete the file
** out from under us.
*/
assert( (PAGER_JOURNALMODE_MEMORY & 5)!=1 );
assert( (PAGER_JOURNALMODE_OFF & 5)!=1 );
assert( (PAGER_JOURNALMODE_WAL & 5)!=1 );
assert( (PAGER_JOURNALMODE_DELETE & 5)!=1 );
assert( (PAGER_JOURNALMODE_TRUNCATE & 5)==1 );
assert( (PAGER_JOURNALMODE_PERSIST & 5)==1 );
if( 0==(iDc & SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN)
|| 1!=(pPager->journalMode & 5)
){
sqlite3OsClose(pPager->jfd);
}
/* If the pager is in the ERROR state and the call to unlock the database
** file fails, set the current lock to UNKNOWN_LOCK. See the comment
** above the #define for UNKNOWN_LOCK for an explanation of why this
** is necessary.
*/
rc = pagerUnlockDb(pPager, NO_LOCK);
if( rc!=SQLITE_OK && pPager->eState==PAGER_ERROR ){
pPager->eLock = UNKNOWN_LOCK;
}
/* The pager state may be changed from PAGER_ERROR to PAGER_OPEN here
** without clearing the error code. This is intentional - the error
** code is cleared and the cache reset in the block below.
*/
assert( pPager->errCode || pPager->eState!=PAGER_ERROR );
pPager->eState = PAGER_OPEN;
}
/* If Pager.errCode is set, the contents of the pager cache cannot be
** trusted. Now that there are no outstanding references to the pager,
** it can safely move back to PAGER_OPEN state. This happens in both
** normal and exclusive-locking mode.
*/
assert( pPager->errCode==SQLITE_OK || !MEMDB );
if( pPager->errCode ){
if( pPager->tempFile==0 ){
pager_reset(pPager);
pPager->changeCountDone = 0;
pPager->eState = PAGER_OPEN;
}else{
pPager->eState = (isOpen(pPager->jfd) ? PAGER_OPEN : PAGER_READER);
}
if( USEFETCH(pPager) ) sqlite3OsUnfetch(pPager->fd, 0, 0);
pPager->errCode = SQLITE_OK;
setGetterMethod(pPager);
}
pPager->journalOff = 0;
pPager->journalHdr = 0;
pPager->setSuper = 0;
}
/*
** This function is called whenever an IOERR or FULL error that requires
** the pager to transition into the ERROR state may have occurred.
** The first argument is a pointer to the pager structure, the second
** the error-code about to be returned by a pager API function. The
** value returned is a copy of the second argument to this function.
**
** If the second argument is SQLITE_FULL, SQLITE_IOERR or one of the
** IOERR sub-codes, the pager enters the ERROR state and the error code
** is stored in Pager.errCode. While the pager remains in the ERROR state,
** all major API calls on the Pager will immediately return Pager.errCode.
**
** The ERROR state indicates that the contents of the pager-cache
** cannot be trusted. This state can be cleared by completely discarding
** the contents of the pager-cache. If a transaction was active when
** the persistent error occurred, then the rollback journal may need
** to be replayed to restore the contents of the database file (as if
** it were a hot-journal).
*/
static int pager_error(Pager *pPager, int rc){
int rc2 = rc & 0xff;
assert( rc==SQLITE_OK || !MEMDB );
assert(
pPager->errCode==SQLITE_FULL ||
pPager->errCode==SQLITE_OK ||
(pPager->errCode & 0xff)==SQLITE_IOERR
);
if( rc2==SQLITE_FULL || rc2==SQLITE_IOERR ){
pPager->errCode = rc;
pPager->eState = PAGER_ERROR;
setGetterMethod(pPager);
}
return rc;
}
static int pager_truncate(Pager *pPager, Pgno nPage);
/*
** The write transaction open on pPager is being committed (bCommit==1)
** or rolled back (bCommit==0).
**
** Return TRUE if and only if all dirty pages should be flushed to disk.
**
** Rules:
**
** * For non-TEMP databases, always sync to disk. This is necessary
** for transactions to be durable.
**
** * Sync TEMP database only on a COMMIT (not a ROLLBACK) when the backing
** file has been created already (via a spill on pagerStress()) and
** when the number of dirty pages in memory exceeds 25% of the total
** cache size.
*/
static int pagerFlushOnCommit(Pager *pPager, int bCommit){
if( pPager->tempFile==0 ) return 1;
if( !bCommit ) return 0;
if( !isOpen(pPager->fd) ) return 0;
return (sqlite3PCachePercentDirty(pPager->pPCache)>=25);
}
/*
** This routine ends a transaction. A transaction is usually ended by
** either a COMMIT or a ROLLBACK operation. This routine may be called
** after rollback of a hot-journal, or if an error occurs while opening
** the journal file or writing the very first journal-header of a
** database transaction.
**
** This routine is never called in PAGER_ERROR state. If it is called
** in PAGER_NONE or PAGER_SHARED state and the lock held is less
** exclusive than a RESERVED lock, it is a no-op.
**
** Otherwise, any active savepoints are released.
**
** If the journal file is open, then it is "finalized". Once a journal
** file has been finalized it is not possible to use it to roll back a
** transaction. Nor will it be considered to be a hot-journal by this
** or any other database connection. Exactly how a journal is finalized
** depends on whether or not the pager is running in exclusive mode and
** the current journal-mode (Pager.journalMode value), as follows:
**
** journalMode==MEMORY
** Journal file descriptor is simply closed. This destroys an
** in-memory journal.
**
** journalMode==TRUNCATE
** Journal file is truncated to zero bytes in size.
**
** journalMode==PERSIST
** The first 28 bytes of the journal file are zeroed. This invalidates
** the first journal header in the file, and hence the entire journal
** file. An invalid journal file cannot be rolled back.
**
** journalMode==DELETE
** The journal file is closed and deleted using sqlite3OsDelete().
**
** If the pager is running in exclusive mode, this method of finalizing
** the journal file is never used. Instead, if the journalMode is
** DELETE and the pager is in exclusive mode, the method described under
** journalMode==PERSIST is used instead.
**
** After the journal is finalized, the pager moves to PAGER_READER state.
** If running in non-exclusive rollback mode, the lock on the file is
** downgraded to a SHARED_LOCK.
**
** SQLITE_OK is returned if no error occurs. If an error occurs during
** any of the IO operations to finalize the journal file or unlock the
** database then the IO error code is returned to the user. If the
** operation to finalize the journal file fails, then the code still
** tries to unlock the database file if not in exclusive mode. If the
** unlock operation fails as well, then the first error code related
** to the first error encountered (the journal finalization one) is
** returned.
*/
static int pager_end_transaction(Pager *pPager, int hasSuper, int bCommit){
int rc = SQLITE_OK; /* Error code from journal finalization operation */
int rc2 = SQLITE_OK; /* Error code from db file unlock operation */
/* Do nothing if the pager does not have an open write transaction
** or at least a RESERVED lock. This function may be called when there
** is no write-transaction active but a RESERVED or greater lock is
** held under two circumstances:
**
** 1. After a successful hot-journal rollback, it is called with
** eState==PAGER_NONE and eLock==EXCLUSIVE_LOCK.
**
** 2. If a connection with locking_mode=exclusive holding an EXCLUSIVE
** lock switches back to locking_mode=normal and then executes a
** read-transaction, this function is called with eState==PAGER_READER
** and eLock==EXCLUSIVE_LOCK when the read-transaction is closed.
*/
assert( assert_pager_state(pPager) );
assert( pPager->eState!=PAGER_ERROR );
if( pPager->eState<PAGER_WRITER_LOCKED && pPager->eLock<RESERVED_LOCK ){
return SQLITE_OK;
}
releaseAllSavepoints(pPager);
assert( isOpen(pPager->jfd) || pPager->pInJournal==0
|| (sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_BATCH_ATOMIC)
);
if( isOpen(pPager->jfd) ){
assert( !pagerUseWal(pPager) );
/* Finalize the journal file. */
if( sqlite3JournalIsInMemory(pPager->jfd) ){
/* assert( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ); */
sqlite3OsClose(pPager->jfd);
}else if( pPager->journalMode==PAGER_JOURNALMODE_TRUNCATE ){
if( pPager->journalOff==0 ){
rc = SQLITE_OK;
}else{
rc = sqlite3OsTruncate(pPager->jfd, 0);
if( rc==SQLITE_OK && pPager->fullSync ){
/* Make sure the new file size is written into the inode right away.
** Otherwise the journal might resurrect following a power loss and
** cause the last transaction to roll back. See
** https://bugzilla.mozilla.org/show_bug.cgi?id=1072773
*/
rc = sqlite3OsSync(pPager->jfd, pPager->syncFlags);
}
}
pPager->journalOff = 0;
}else if( pPager->journalMode==PAGER_JOURNALMODE_PERSIST
|| (pPager->exclusiveMode && pPager->journalMode!=PAGER_JOURNALMODE_WAL)
){
rc = zeroJournalHdr(pPager, hasSuper||pPager->tempFile);
pPager->journalOff = 0;
}else{
/* This branch may be executed with Pager.journalMode==MEMORY if
** a hot-journal was just rolled back. In this case the journal
** file should be closed and deleted. If this connection writes to
** the database file, it will do so using an in-memory journal.
*/
int bDelete = !pPager->tempFile;
assert( sqlite3JournalIsInMemory(pPager->jfd)==0 );
assert( pPager->journalMode==PAGER_JOURNALMODE_DELETE
|| pPager->journalMode==PAGER_JOURNALMODE_MEMORY
|| pPager->journalMode==PAGER_JOURNALMODE_WAL
);
sqlite3OsClose(pPager->jfd);
if( bDelete ){
rc = sqlite3OsDelete(pPager->pVfs, pPager->zJournal, pPager->extraSync);
}
}
}
#ifdef SQLITE_CHECK_PAGES
sqlite3PcacheIterateDirty(pPager->pPCache, pager_set_pagehash);
if( pPager->dbSize==0 && sqlite3PcacheRefCount(pPager->pPCache)>0 ){
PgHdr *p = sqlite3PagerLookup(pPager, 1);
if( p ){
p->pageHash = 0;
sqlite3PagerUnrefNotNull(p);
}
}
#endif
sqlite3BitvecDestroy(pPager->pInJournal);
pPager->pInJournal = 0;
pPager->nRec = 0;
if( rc==SQLITE_OK ){
if( MEMDB || pagerFlushOnCommit(pPager, bCommit) ){
sqlite3PcacheCleanAll(pPager->pPCache);
}else{
sqlite3PcacheClearWritable(pPager->pPCache);
}
sqlite3PcacheTruncate(pPager->pPCache, pPager->dbSize);
}
if( pagerUseWal(pPager) ){
/* Drop the WAL write-lock, if any. Also, if the connection was in
** locking_mode=exclusive mode but is no longer, drop the EXCLUSIVE
** lock held on the database file.
*/
rc2 = sqlite3WalEndWriteTransaction(pPager->pWal);
assert( rc2==SQLITE_OK );
}else if( rc==SQLITE_OK && bCommit && pPager->dbFileSize>pPager->dbSize ){
/* This branch is taken when committing a transaction in rollback-journal
** mode if the database file on disk is larger than the database image.
** At this point the journal has been finalized and the transaction
** successfully committed, but the EXCLUSIVE lock is still held on the
** file. So it is safe to truncate the database file to its minimum
** required size. */
assert( pPager->eLock==EXCLUSIVE_LOCK );
rc = pager_truncate(pPager, pPager->dbSize);
}
if( rc==SQLITE_OK && bCommit ){
rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_COMMIT_PHASETWO, 0);
if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK;
}
if( !pPager->exclusiveMode
&& (!pagerUseWal(pPager) || sqlite3WalExclusiveMode(pPager->pWal, 0))
){
rc2 = pagerUnlockDb(pPager, SHARED_LOCK);
}
pPager->eState = PAGER_READER;
pPager->setSuper = 0;
return (rc==SQLITE_OK?rc2:rc);
}
/* Forward reference */
static int pager_playback(Pager *pPager, int isHot);
/*
** Execute a rollback if a transaction is active and unlock the
** database file.
**
** If the pager has already entered the ERROR state, do not attempt
** the rollback at this time. Instead, pager_unlock() is called. The
** call to pager_unlock() will discard all in-memory pages, unlock
** the database file and move the pager back to OPEN state. If this
** means that there is a hot-journal left in the file-system, the next
** connection to obtain a shared lock on the pager (which may be this one)
** will roll it back.
**
** If the pager has not already entered the ERROR state, but an IO or
** malloc error occurs during a rollback, then this will itself cause
** the pager to enter the ERROR state. Which will be cleared by the
** call to pager_unlock(), as described above.
*/
static void pagerUnlockAndRollback(Pager *pPager){
if( pPager->eState!=PAGER_ERROR && pPager->eState!=PAGER_OPEN ){
assert( assert_pager_state(pPager) );
if( pPager->eState>=PAGER_WRITER_LOCKED ){
sqlite3BeginBenignMalloc();
sqlite3PagerRollback(pPager);
sqlite3EndBenignMalloc();
}else if( !pPager->exclusiveMode ){
assert( pPager->eState==PAGER_READER );
pager_end_transaction(pPager, 0, 0);
}
}else if( pPager->eState==PAGER_ERROR
&& pPager->journalMode==PAGER_JOURNALMODE_MEMORY
&& isOpen(pPager->jfd)
){
/* Special case for a ROLLBACK due to I/O error with an in-memory
** journal: We have to rollback immediately, before the journal is
** closed, because once it is closed, all content is forgotten. */
int errCode = pPager->errCode;
u8 eLock = pPager->eLock;
pPager->eState = PAGER_OPEN;
pPager->errCode = SQLITE_OK;
pPager->eLock = EXCLUSIVE_LOCK;
pager_playback(pPager, 1);
pPager->errCode = errCode;
pPager->eLock = eLock;
}
pager_unlock(pPager);
}
/*
** Parameter aData must point to a buffer of pPager->pageSize bytes
** of data. Compute and return a checksum based on the contents of the
** page of data and the current value of pPager->cksumInit.
**
** This is not a real checksum. It is really just the sum of the
** random initial value (pPager->cksumInit) and every 200th byte
** of the page data, starting with byte offset (pPager->pageSize%200).
** Each byte is interpreted as an 8-bit unsigned integer.
**
** Changing the formula used to compute this checksum results in an
** incompatible journal file format.
**
** If journal corruption occurs due to a power failure, the most likely
** scenario is that one end or the other of the record will be changed.
** It is much less likely that the two ends of the journal record will be
** correct and the middle be corrupt. Thus, this "checksum" scheme,
** though fast and simple, catches the mostly likely kind of corruption.
*/
static u32 pager_cksum(Pager *pPager, const u8 *aData){
u32 cksum = pPager->cksumInit; /* Checksum value to return */
int i = pPager->pageSize-200; /* Loop counter */
while( i>0 ){
cksum += aData[i];
i -= 200;
}
return cksum;
}
/*
** Read a single page from either the journal file (if isMainJrnl==1) or
** from the sub-journal (if isMainJrnl==0) and playback that page.
** The page begins at offset *pOffset into the file. The *pOffset
** value is increased to the start of the next page in the journal.
**
** The main rollback journal uses checksums - the statement journal does
** not.
**
** If the page number of the page record read from the (sub-)journal file
** is greater than the current value of Pager.dbSize, then playback is
** skipped and SQLITE_OK is returned.
**
** If pDone is not NULL, then it is a record of pages that have already
** been played back. If the page at *pOffset has already been played back
** (if the corresponding pDone bit is set) then skip the playback.
** Make sure the pDone bit corresponding to the *pOffset page is set
** prior to returning.
**
** If the page record is successfully read from the (sub-)journal file
** and played back, then SQLITE_OK is returned. If an IO error occurs
** while reading the record from the (sub-)journal file or while writing
** to the database file, then the IO error code is returned. If data
** is successfully read from the (sub-)journal file but appears to be
** corrupted, SQLITE_DONE is returned. Data is considered corrupted in
** two circumstances:
**
** * If the record page-number is illegal (0 or PAGER_SJ_PGNO), or
** * If the record is being rolled back from the main journal file
** and the checksum field does not match the record content.
**
** Neither of these two scenarios are possible during a savepoint rollback.
**
** If this is a savepoint rollback, then memory may have to be dynamically
** allocated by this function. If this is the case and an allocation fails,
** SQLITE_NOMEM is returned.
*/
static int pager_playback_one_page(
Pager *pPager, /* The pager being played back */
i64 *pOffset, /* Offset of record to playback */
Bitvec *pDone, /* Bitvec of pages already played back */
int isMainJrnl, /* 1 -> main journal. 0 -> sub-journal. */
int isSavepnt /* True for a savepoint rollback */
){
int rc;
PgHdr *pPg; /* An existing page in the cache */
Pgno pgno; /* The page number of a page in journal */
u32 cksum; /* Checksum used for sanity checking */
char *aData; /* Temporary storage for the page */
sqlite3_file *jfd; /* The file descriptor for the journal file */
int isSynced; /* True if journal page is synced */
assert( (isMainJrnl&~1)==0 ); /* isMainJrnl is 0 or 1 */
assert( (isSavepnt&~1)==0 ); /* isSavepnt is 0 or 1 */
assert( isMainJrnl || pDone ); /* pDone always used on sub-journals */
assert( isSavepnt || pDone==0 ); /* pDone never used on non-savepoint */
aData = pPager->pTmpSpace;
assert( aData ); /* Temp storage must have already been allocated */
assert( pagerUseWal(pPager)==0 || (!isMainJrnl && isSavepnt) );
/* Either the state is greater than PAGER_WRITER_CACHEMOD (a transaction
** or savepoint rollback done at the request of the caller) or this is
** a hot-journal rollback. If it is a hot-journal rollback, the pager
** is in state OPEN and holds an EXCLUSIVE lock. Hot-journal rollback
** only reads from the main journal, not the sub-journal.
*/
assert( pPager->eState>=PAGER_WRITER_CACHEMOD
|| (pPager->eState==PAGER_OPEN && pPager->eLock==EXCLUSIVE_LOCK)
);
assert( pPager->eState>=PAGER_WRITER_CACHEMOD || isMainJrnl );
/* Read the page number and page data from the journal or sub-journal
** file. Return an error code to the caller if an IO error occurs.
*/
jfd = isMainJrnl ? pPager->jfd : pPager->sjfd;
rc = read32bits(jfd, *pOffset, &pgno);
if( rc!=SQLITE_OK ) return rc;
rc = sqlite3OsRead(jfd, (u8*)aData, pPager->pageSize, (*pOffset)+4);
if( rc!=SQLITE_OK ) return rc;
*pOffset += pPager->pageSize + 4 + isMainJrnl*4;
/* Sanity checking on the page. This is more important that I originally
** thought. If a power failure occurs while the journal is being written,
** it could cause invalid data to be written into the journal. We need to
** detect this invalid data (with high probability) and ignore it.
*/
if( pgno==0 || pgno==PAGER_SJ_PGNO(pPager) ){
assert( !isSavepnt );
return SQLITE_DONE;
}
if( pgno>(Pgno)pPager->dbSize || sqlite3BitvecTest(pDone, pgno) ){
return SQLITE_OK;
}
if( isMainJrnl ){
rc = read32bits(jfd, (*pOffset)-4, &cksum);
if( rc ) return rc;
if( !isSavepnt && pager_cksum(pPager, (u8*)aData)!=cksum ){
return SQLITE_DONE;
}
}
/* If this page has already been played back before during the current
** rollback, then don't bother to play it back again.
*/
if( pDone && (rc = sqlite3BitvecSet(pDone, pgno))!=SQLITE_OK ){
return rc;
}
/* When playing back page 1, restore the nReserve setting
*/
if( pgno==1 && pPager->nReserve!=((u8*)aData)[20] ){
pPager->nReserve = ((u8*)aData)[20];
}
/* If the pager is in CACHEMOD state, then there must be a copy of this
** page in the pager cache. In this case just update the pager cache,
** not the database file. The page is left marked dirty in this case.
**
** An exception to the above rule: If the database is in no-sync mode
** and a page is moved during an incremental vacuum then the page may
** not be in the pager cache. Later: if a malloc() or IO error occurs
** during a Movepage() call, then the page may not be in the cache
** either. So the condition described in the above paragraph is not
** assert()able.
**
** If in WRITER_DBMOD, WRITER_FINISHED or OPEN state, then we update the
** pager cache if it exists and the main file. The page is then marked
** not dirty. Since this code is only executed in PAGER_OPEN state for
** a hot-journal rollback, it is guaranteed that the page-cache is empty
** if the pager is in OPEN state.
**
** Ticket #1171: The statement journal might contain page content that is
** different from the page content at the start of the transaction.
** This occurs when a page is changed prior to the start of a statement
** then changed again within the statement. When rolling back such a
** statement we must not write to the original database unless we know
** for certain that original page contents are synced into the main rollback
** journal. Otherwise, a power loss might leave modified data in the
** database file without an entry in the rollback journal that can
** restore the database to its original form. Two conditions must be
** met before writing to the database files. (1) the database must be
** locked. (2) we know that the original page content is fully synced
** in the main journal either because the page is not in cache or else
** the page is marked as needSync==0.
**
** 2008-04-14: When attempting to vacuum a corrupt database file, it
** is possible to fail a statement on a database that does not yet exist.
** Do not attempt to write if database file has never been opened.
*/
if( pagerUseWal(pPager) ){
pPg = 0;
}else{
pPg = sqlite3PagerLookup(pPager, pgno);
}
assert( pPg || !MEMDB );
assert( pPager->eState!=PAGER_OPEN || pPg==0 || pPager->tempFile );
PAGERTRACE(("PLAYBACK %d page %d hash(%08x) %s\n",
PAGERID(pPager), pgno, pager_datahash(pPager->pageSize, (u8*)aData),
(isMainJrnl?"main-journal":"sub-journal")
));
if( isMainJrnl ){
isSynced = pPager->noSync || (*pOffset <= pPager->journalHdr);
}else{
isSynced = (pPg==0 || 0==(pPg->flags & PGHDR_NEED_SYNC));
}
if( isOpen(pPager->fd)
&& (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN)
&& isSynced
){
i64 ofst = (pgno-1)*(i64)pPager->pageSize;
testcase( !isSavepnt && pPg!=0 && (pPg->flags&PGHDR_NEED_SYNC)!=0 );
assert( !pagerUseWal(pPager) );
/* Write the data read from the journal back into the database file.
** This is usually safe even for an encrypted database - as the data
** was encrypted before it was written to the journal file. The exception
** is if the data was just read from an in-memory sub-journal. In that
** case it must be encrypted here before it is copied into the database
** file. */
rc = sqlite3OsWrite(pPager->fd, (u8 *)aData, pPager->pageSize, ofst);
if( pgno>pPager->dbFileSize ){
pPager->dbFileSize = pgno;
}
if( pPager->pBackup ){
sqlite3BackupUpdate(pPager->pBackup, pgno, (u8*)aData);
}
}else if( !isMainJrnl && pPg==0 ){
/* If this is a rollback of a savepoint and data was not written to
** the database and the page is not in-memory, there is a potential
** problem. When the page is next fetched by the b-tree layer, it
** will be read from the database file, which may or may not be
** current.
**
** There are a couple of different ways this can happen. All are quite
** obscure. When running in synchronous mode, this can only happen
** if the page is on the free-list at the start of the transaction, then
** populated, then moved using sqlite3PagerMovepage().
**
** The solution is to add an in-memory page to the cache containing
** the data just read from the sub-journal. Mark the page as dirty
** and if the pager requires a journal-sync, then mark the page as
** requiring a journal-sync before it is written.
*/
assert( isSavepnt );
assert( (pPager->doNotSpill & SPILLFLAG_ROLLBACK)==0 );
pPager->doNotSpill |= SPILLFLAG_ROLLBACK;
rc = sqlite3PagerGet(pPager, pgno, &pPg, 1);
assert( (pPager->doNotSpill & SPILLFLAG_ROLLBACK)!=0 );
pPager->doNotSpill &= ~SPILLFLAG_ROLLBACK;
if( rc!=SQLITE_OK ) return rc;
sqlite3PcacheMakeDirty(pPg);
}
if( pPg ){
/* No page should ever be explicitly rolled back that is in use, except
** for page 1 which is held in use in order to keep the lock on the
** database active. However such a page may be rolled back as a result
** of an internal error resulting in an automatic call to
** sqlite3PagerRollback().
*/
void *pData;
pData = pPg->pData;
memcpy(pData, (u8*)aData, pPager->pageSize);
pPager->xReiniter(pPg);
/* It used to be that sqlite3PcacheMakeClean(pPg) was called here. But
** that call was dangerous and had no detectable benefit since the cache
** is normally cleaned by sqlite3PcacheCleanAll() after rollback and so
** has been removed. */
pager_set_pagehash(pPg);
/* If this was page 1, then restore the value of Pager.dbFileVers.
** Do this before any decoding. */
if( pgno==1 ){
memcpy(&pPager->dbFileVers, &((u8*)pData)[24],sizeof(pPager->dbFileVers));
}
sqlite3PcacheRelease(pPg);
}
return rc;
}
/*
** Parameter zSuper is the name of a super-journal file. A single journal
** file that referred to the super-journal file has just been rolled back.
** This routine checks if it is possible to delete the super-journal file,
** and does so if it is.
**
** Argument zSuper may point to Pager.pTmpSpace. So that buffer is not
** available for use within this function.
**
** When a super-journal file is created, it is populated with the names
** of all of its child journals, one after another, formatted as utf-8
** encoded text. The end of each child journal file is marked with a
** nul-terminator byte (0x00). i.e. the entire contents of a super-journal
** file for a transaction involving two databases might be:
**
** "/home/bill/a.db-journal\x00/home/bill/b.db-journal\x00"
**
** A super-journal file may only be deleted once all of its child
** journals have been rolled back.
**
** This function reads the contents of the super-journal file into
** memory and loops through each of the child journal names. For
** each child journal, it checks if:
**
** * if the child journal exists, and if so
** * if the child journal contains a reference to super-journal
** file zSuper
**
** If a child journal can be found that matches both of the criteria
** above, this function returns without doing anything. Otherwise, if
** no such child journal can be found, file zSuper is deleted from
** the file-system using sqlite3OsDelete().
**
** If an IO error within this function, an error code is returned. This
** function allocates memory by calling sqlite3Malloc(). If an allocation
** fails, SQLITE_NOMEM is returned. Otherwise, if no IO or malloc errors
** occur, SQLITE_OK is returned.
**
** TODO: This function allocates a single block of memory to load
** the entire contents of the super-journal file. This could be
** a couple of kilobytes or so - potentially larger than the page
** size.
*/
static int pager_delsuper(Pager *pPager, const char *zSuper){
sqlite3_vfs *pVfs = pPager->pVfs;
int rc; /* Return code */
sqlite3_file *pSuper; /* Malloc'd super-journal file descriptor */
sqlite3_file *pJournal; /* Malloc'd child-journal file descriptor */
char *zSuperJournal = 0; /* Contents of super-journal file */
i64 nSuperJournal; /* Size of super-journal file */
char *zJournal; /* Pointer to one journal within MJ file */
char *zSuperPtr; /* Space to hold super-journal filename */
char *zFree = 0; /* Free this buffer */
int nSuperPtr; /* Amount of space allocated to zSuperPtr[] */
/* Allocate space for both the pJournal and pSuper file descriptors.
** If successful, open the super-journal file for reading.
*/
pSuper = (sqlite3_file *)sqlite3MallocZero(pVfs->szOsFile * 2);
if( !pSuper ){
rc = SQLITE_NOMEM_BKPT;
pJournal = 0;
}else{
const int flags = (SQLITE_OPEN_READONLY|SQLITE_OPEN_SUPER_JOURNAL);
rc = sqlite3OsOpen(pVfs, zSuper, pSuper, flags, 0);
pJournal = (sqlite3_file *)(((u8 *)pSuper) + pVfs->szOsFile);
}
if( rc!=SQLITE_OK ) goto delsuper_out;
/* Load the entire super-journal file into space obtained from
** sqlite3_malloc() and pointed to by zSuperJournal. Also obtain
** sufficient space (in zSuperPtr) to hold the names of super-journal
** files extracted from regular rollback-journals.
*/
rc = sqlite3OsFileSize(pSuper, &nSuperJournal);
if( rc!=SQLITE_OK ) goto delsuper_out;
nSuperPtr = pVfs->mxPathname+1;
zFree = sqlite3Malloc(4 + nSuperJournal + nSuperPtr + 2);
if( !zFree ){
rc = SQLITE_NOMEM_BKPT;
goto delsuper_out;
}
zFree[0] = zFree[1] = zFree[2] = zFree[3] = 0;
zSuperJournal = &zFree[4];
zSuperPtr = &zSuperJournal[nSuperJournal+2];
rc = sqlite3OsRead(pSuper, zSuperJournal, (int)nSuperJournal, 0);
if( rc!=SQLITE_OK ) goto delsuper_out;
zSuperJournal[nSuperJournal] = 0;
zSuperJournal[nSuperJournal+1] = 0;
zJournal = zSuperJournal;
while( (zJournal-zSuperJournal)<nSuperJournal ){
int exists;
rc = sqlite3OsAccess(pVfs, zJournal, SQLITE_ACCESS_EXISTS, &exists);
if( rc!=SQLITE_OK ){
goto delsuper_out;
}
if( exists ){
/* One of the journals pointed to by the super-journal exists.
** Open it and check if it points at the super-journal. If
** so, return without deleting the super-journal file.
** NB: zJournal is really a MAIN_JOURNAL. But call it a
** SUPER_JOURNAL here so that the VFS will not send the zJournal
** name into sqlite3_database_file_object().
*/
int c;
int flags = (SQLITE_OPEN_READONLY|SQLITE_OPEN_SUPER_JOURNAL);
rc = sqlite3OsOpen(pVfs, zJournal, pJournal, flags, 0);
if( rc!=SQLITE_OK ){
goto delsuper_out;
}
rc = readSuperJournal(pJournal, zSuperPtr, nSuperPtr);
sqlite3OsClose(pJournal);
if( rc!=SQLITE_OK ){
goto delsuper_out;
}
c = zSuperPtr[0]!=0 && strcmp(zSuperPtr, zSuper)==0;
if( c ){
/* We have a match. Do not delete the super-journal file. */
goto delsuper_out;
}
}
zJournal += (sqlite3Strlen30(zJournal)+1);
}
sqlite3OsClose(pSuper);
rc = sqlite3OsDelete(pVfs, zSuper, 0);
delsuper_out:
sqlite3_free(zFree);
if( pSuper ){
sqlite3OsClose(pSuper);
assert( !isOpen(pJournal) );
sqlite3_free(pSuper);
}
return rc;
}
/*
** This function is used to change the actual size of the database
** file in the file-system. This only happens when committing a transaction,
** or rolling back a transaction (including rolling back a hot-journal).
**
** If the main database file is not open, or the pager is not in either
** DBMOD or OPEN state, this function is a no-op. Otherwise, the size
** of the file is changed to nPage pages (nPage*pPager->pageSize bytes).
** If the file on disk is currently larger than nPage pages, then use the VFS
** xTruncate() method to truncate it.
**
** Or, it might be the case that the file on disk is smaller than
** nPage pages. Some operating system implementations can get confused if
** you try to truncate a file to some size that is larger than it
** currently is, so detect this case and write a single zero byte to
** the end of the new file instead.
**
** If successful, return SQLITE_OK. If an IO error occurs while modifying
** the database file, return the error code to the caller.
*/
static int pager_truncate(Pager *pPager, Pgno nPage){
int rc = SQLITE_OK;
assert( pPager->eState!=PAGER_ERROR );
assert( pPager->eState!=PAGER_READER );
PAGERTRACE(("Truncate %d npage %u\n", PAGERID(pPager), nPage));
if( isOpen(pPager->fd)
&& (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN)
){
i64 currentSize, newSize;
int szPage = pPager->pageSize;
assert( pPager->eLock==EXCLUSIVE_LOCK );
/* TODO: Is it safe to use Pager.dbFileSize here? */
rc = sqlite3OsFileSize(pPager->fd, &currentSize);
newSize = szPage*(i64)nPage;
if( rc==SQLITE_OK && currentSize!=newSize ){
if( currentSize>newSize ){
rc = sqlite3OsTruncate(pPager->fd, newSize);
}else if( (currentSize+szPage)<=newSize ){
char *pTmp = pPager->pTmpSpace;
memset(pTmp, 0, szPage);
testcase( (newSize-szPage) == currentSize );
testcase( (newSize-szPage) > currentSize );
sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_SIZE_HINT, &newSize);
rc = sqlite3OsWrite(pPager->fd, pTmp, szPage, newSize-szPage);
}
if( rc==SQLITE_OK ){
pPager->dbFileSize = nPage;
}
}
}
return rc;
}
/*
** Return a sanitized version of the sector-size of OS file pFile. The
** return value is guaranteed to lie between 32 and MAX_SECTOR_SIZE.
*/
int sqlite3SectorSize(sqlite3_file *pFile){
int iRet = sqlite3OsSectorSize(pFile);
if( iRet<32 ){
iRet = 512;
}else if( iRet>MAX_SECTOR_SIZE ){
assert( MAX_SECTOR_SIZE>=512 );
iRet = MAX_SECTOR_SIZE;
}
return iRet;
}
/*
** Set the value of the Pager.sectorSize variable for the given
** pager based on the value returned by the xSectorSize method
** of the open database file. The sector size will be used
** to determine the size and alignment of journal header and
** super-journal pointers within created journal files.
**
** For temporary files the effective sector size is always 512 bytes.
**
** Otherwise, for non-temporary files, the effective sector size is
** the value returned by the xSectorSize() method rounded up to 32 if
** it is less than 32, or rounded down to MAX_SECTOR_SIZE if it
** is greater than MAX_SECTOR_SIZE.
**
** If the file has the SQLITE_IOCAP_POWERSAFE_OVERWRITE property, then set
** the effective sector size to its minimum value (512). The purpose of
** pPager->sectorSize is to define the "blast radius" of bytes that
** might change if a crash occurs while writing to a single byte in
** that range. But with POWERSAFE_OVERWRITE, the blast radius is zero
** (that is what POWERSAFE_OVERWRITE means), so we minimize the sector
** size. For backwards compatibility of the rollback journal file format,
** we cannot reduce the effective sector size below 512.
*/
static void setSectorSize(Pager *pPager){
assert( isOpen(pPager->fd) || pPager->tempFile );
if( pPager->tempFile
|| (sqlite3OsDeviceCharacteristics(pPager->fd) &
SQLITE_IOCAP_POWERSAFE_OVERWRITE)!=0
){
/* Sector size doesn't matter for temporary files. Also, the file
** may not have been opened yet, in which case the OsSectorSize()
** call will segfault. */
pPager->sectorSize = 512;
}else{
pPager->sectorSize = sqlite3SectorSize(pPager->fd);
}
}
/*
** Playback the journal and thus restore the database file to
** the state it was in before we started making changes.
**
** The journal file format is as follows:
**
** (1) 8 byte prefix. A copy of aJournalMagic[].
** (2) 4 byte big-endian integer which is the number of valid page records
** in the journal. If this value is 0xffffffff, then compute the
** number of page records from the journal size.
** (3) 4 byte big-endian integer which is the initial value for the
** sanity checksum.
** (4) 4 byte integer which is the number of pages to truncate the
** database to during a rollback.
** (5) 4 byte big-endian integer which is the sector size. The header
** is this many bytes in size.
** (6) 4 byte big-endian integer which is the page size.
** (7) zero padding out to the next sector size.
** (8) Zero or more pages instances, each as follows:
** + 4 byte page number.
** + pPager->pageSize bytes of data.
** + 4 byte checksum
**
** When we speak of the journal header, we mean the first 7 items above.
** Each entry in the journal is an instance of the 8th item.
**
** Call the value from the second bullet "nRec". nRec is the number of
** valid page entries in the journal. In most cases, you can compute the
** value of nRec from the size of the journal file. But if a power
** failure occurred while the journal was being written, it could be the
** case that the size of the journal file had already been increased but
** the extra entries had not yet made it safely to disk. In such a case,
** the value of nRec computed from the file size would be too large. For
** that reason, we always use the nRec value in the header.
**
** If the nRec value is 0xffffffff it means that nRec should be computed
** from the file size. This value is used when the user selects the
** no-sync option for the journal. A power failure could lead to corruption
** in this case. But for things like temporary table (which will be
** deleted when the power is restored) we don't care.
**
** If the file opened as the journal file is not a well-formed
** journal file then all pages up to the first corrupted page are rolled
** back (or no pages if the journal header is corrupted). The journal file
** is then deleted and SQLITE_OK returned, just as if no corruption had
** been encountered.
**
** If an I/O or malloc() error occurs, the journal-file is not deleted
** and an error code is returned.
**
** The isHot parameter indicates that we are trying to rollback a journal
** that might be a hot journal. Or, it could be that the journal is
** preserved because of JOURNALMODE_PERSIST or JOURNALMODE_TRUNCATE.
** If the journal really is hot, reset the pager cache prior rolling
** back any content. If the journal is merely persistent, no reset is
** needed.
*/
static int pager_playback(Pager *pPager, int isHot){
sqlite3_vfs *pVfs = pPager->pVfs;
i64 szJ; /* Size of the journal file in bytes */
u32 nRec; /* Number of Records in the journal */
u32 u; /* Unsigned loop counter */
Pgno mxPg = 0; /* Size of the original file in pages */
int rc; /* Result code of a subroutine */
int res = 1; /* Value returned by sqlite3OsAccess() */
char *zSuper = 0; /* Name of super-journal file if any */
int needPagerReset; /* True to reset page prior to first page rollback */
int nPlayback = 0; /* Total number of pages restored from journal */
u32 savedPageSize = pPager->pageSize;
/* Figure out how many records are in the journal. Abort early if
** the journal is empty.
*/
assert( isOpen(pPager->jfd) );
rc = sqlite3OsFileSize(pPager->jfd, &szJ);
if( rc!=SQLITE_OK ){
goto end_playback;
}
/* Read the super-journal name from the journal, if it is present.
** If a super-journal file name is specified, but the file is not
** present on disk, then the journal is not hot and does not need to be
** played back.
**
** TODO: Technically the following is an error because it assumes that
** buffer Pager.pTmpSpace is (mxPathname+1) bytes or larger. i.e. that
** (pPager->pageSize >= pPager->pVfs->mxPathname+1). Using os_unix.c,
** mxPathname is 512, which is the same as the minimum allowable value
** for pageSize.
*/
zSuper = pPager->pTmpSpace;
rc = readSuperJournal(pPager->jfd, zSuper, pPager->pVfs->mxPathname+1);
if( rc==SQLITE_OK && zSuper[0] ){
rc = sqlite3OsAccess(pVfs, zSuper, SQLITE_ACCESS_EXISTS, &res);
}
zSuper = 0;
if( rc!=SQLITE_OK || !res ){
goto end_playback;
}
pPager->journalOff = 0;
needPagerReset = isHot;
/* This loop terminates either when a readJournalHdr() or
** pager_playback_one_page() call returns SQLITE_DONE or an IO error
** occurs.
*/
while( 1 ){
/* Read the next journal header from the journal file. If there are
** not enough bytes left in the journal file for a complete header, or
** it is corrupted, then a process must have failed while writing it.
** This indicates nothing more needs to be rolled back.
*/
rc = readJournalHdr(pPager, isHot, szJ, &nRec, &mxPg);
if( rc!=SQLITE_OK ){
if( rc==SQLITE_DONE ){
rc = SQLITE_OK;
}
goto end_playback;
}
/* If nRec is 0xffffffff, then this journal was created by a process
** working in no-sync mode. This means that the rest of the journal
** file consists of pages, there are no more journal headers. Compute
** the value of nRec based on this assumption.
*/
if( nRec==0xffffffff ){
assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) );
nRec = (int)((szJ - JOURNAL_HDR_SZ(pPager))/JOURNAL_PG_SZ(pPager));
}
/* If nRec is 0 and this rollback is of a transaction created by this
** process and if this is the final header in the journal, then it means
** that this part of the journal was being filled but has not yet been
** synced to disk. Compute the number of pages based on the remaining
** size of the file.
**
** The third term of the test was added to fix ticket #2565.
** When rolling back a hot journal, nRec==0 always means that the next
** chunk of the journal contains zero pages to be rolled back. But
** when doing a ROLLBACK and the nRec==0 chunk is the last chunk in
** the journal, it means that the journal might contain additional
** pages that need to be rolled back and that the number of pages
** should be computed based on the journal file size.
*/
if( nRec==0 && !isHot &&
pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff ){
nRec = (int)((szJ - pPager->journalOff) / JOURNAL_PG_SZ(pPager));
}
/* If this is the first header read from the journal, truncate the
** database file back to its original size.
*/
if( pPager->journalOff==JOURNAL_HDR_SZ(pPager) ){
rc = pager_truncate(pPager, mxPg);
if( rc!=SQLITE_OK ){
goto end_playback;
}
pPager->dbSize = mxPg;
if( pPager->mxPgno<mxPg ){
pPager->mxPgno = mxPg;
}
}
/* Copy original pages out of the journal and back into the
** database file and/or page cache.
*/
for(u=0; u<nRec; u++){
if( needPagerReset ){
pager_reset(pPager);
needPagerReset = 0;
}
rc = pager_playback_one_page(pPager,&pPager->journalOff,0,1,0);
if( rc==SQLITE_OK ){
nPlayback++;
}else{
if( rc==SQLITE_DONE ){
pPager->journalOff = szJ;
break;
}else if( rc==SQLITE_IOERR_SHORT_READ ){
/* If the journal has been truncated, simply stop reading and
** processing the journal. This might happen if the journal was
** not completely written and synced prior to a crash. In that
** case, the database should have never been written in the
** first place so it is OK to simply abandon the rollback. */
rc = SQLITE_OK;
goto end_playback;
}else{
/* If we are unable to rollback, quit and return the error
** code. This will cause the pager to enter the error state
** so that no further harm will be done. Perhaps the next
** process to come along will be able to rollback the database.
*/
goto end_playback;
}
}
}
}
/*NOTREACHED*/
assert( 0 );
end_playback:
if( rc==SQLITE_OK ){
rc = sqlite3PagerSetPagesize(pPager, &savedPageSize, -1);
}
/* Following a rollback, the database file should be back in its original
** state prior to the start of the transaction, so invoke the
** SQLITE_FCNTL_DB_UNCHANGED file-control method to disable the
** assertion that the transaction counter was modified.
*/
#ifdef SQLITE_DEBUG
sqlite3OsFileControlHint(pPager->fd,SQLITE_FCNTL_DB_UNCHANGED,0);
#endif
/* If this playback is happening automatically as a result of an IO or
** malloc error that occurred after the change-counter was updated but
** before the transaction was committed, then the change-counter
** modification may just have been reverted. If this happens in exclusive
** mode, then subsequent transactions performed by the connection will not
** update the change-counter at all. This may lead to cache inconsistency
** problems for other processes at some point in the future. So, just
** in case this has happened, clear the changeCountDone flag now.
*/
pPager->changeCountDone = pPager->tempFile;
if( rc==SQLITE_OK ){
/* Leave 4 bytes of space before the super-journal filename in memory.
** This is because it may end up being passed to sqlite3OsOpen(), in
** which case it requires 4 0x00 bytes in memory immediately before
** the filename. */
zSuper = &pPager->pTmpSpace[4];
rc = readSuperJournal(pPager->jfd, zSuper, pPager->pVfs->mxPathname+1);
testcase( rc!=SQLITE_OK );
}
if( rc==SQLITE_OK
&& (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN)
){
rc = sqlite3PagerSync(pPager, 0);
}
if( rc==SQLITE_OK ){
rc = pager_end_transaction(pPager, zSuper[0]!='\0', 0);
testcase( rc!=SQLITE_OK );
}
if( rc==SQLITE_OK && zSuper[0] && res ){
/* If there was a super-journal and this routine will return success,
** see if it is possible to delete the super-journal.
*/
assert( zSuper==&pPager->pTmpSpace[4] );
memset(pPager->pTmpSpace, 0, 4);
rc = pager_delsuper(pPager, zSuper);
testcase( rc!=SQLITE_OK );
}
if( isHot && nPlayback ){
sqlite3_log(SQLITE_NOTICE_RECOVER_ROLLBACK, "recovered %d pages from %s",
nPlayback, pPager->zJournal);
}
/* The Pager.sectorSize variable may have been updated while rolling
** back a journal created by a process with a different sector size
** value. Reset it to the correct value for this process.
*/
setSectorSize(pPager);
return rc;
}
/*
** Read the content for page pPg out of the database file (or out of
** the WAL if that is where the most recent copy if found) into
** pPg->pData. A shared lock or greater must be held on the database
** file before this function is called.
**
** If page 1 is read, then the value of Pager.dbFileVers[] is set to
** the value read from the database file.
**
** If an IO error occurs, then the IO error is returned to the caller.
** Otherwise, SQLITE_OK is returned.
*/
static int readDbPage(PgHdr *pPg){
Pager *pPager = pPg->pPager; /* Pager object associated with page pPg */
int rc = SQLITE_OK; /* Return code */
#ifndef SQLITE_OMIT_WAL
u32 iFrame = 0; /* Frame of WAL containing pgno */
assert( pPager->eState>=PAGER_READER && !MEMDB );
assert( isOpen(pPager->fd) );
if( pagerUseWal(pPager) ){
rc = sqlite3WalFindFrame(pPager->pWal, pPg->pgno, &iFrame);
if( rc ) return rc;
}
if( iFrame ){
rc = sqlite3WalReadFrame(pPager->pWal, iFrame,pPager->pageSize,pPg->pData);
}else
#endif
{
i64 iOffset = (pPg->pgno-1)*(i64)pPager->pageSize;
rc = sqlite3OsRead(pPager->fd, pPg->pData, pPager->pageSize, iOffset);
if( rc==SQLITE_IOERR_SHORT_READ ){
rc = SQLITE_OK;
}
}
if( pPg->pgno==1 ){
if( rc ){
/* If the read is unsuccessful, set the dbFileVers[] to something
** that will never be a valid file version. dbFileVers[] is a copy
** of bytes 24..39 of the database. Bytes 28..31 should always be
** zero or the size of the database in page. Bytes 32..35 and 35..39
** should be page numbers which are never 0xffffffff. So filling
** pPager->dbFileVers[] with all 0xff bytes should suffice.
**
** For an encrypted database, the situation is more complex: bytes
** 24..39 of the database are white noise. But the probability of
** white noise equaling 16 bytes of 0xff is vanishingly small so
** we should still be ok.
*/
memset(pPager->dbFileVers, 0xff, sizeof(pPager->dbFileVers));
}else{
u8 *dbFileVers = &((u8*)pPg->pData)[24];
memcpy(&pPager->dbFileVers, dbFileVers, sizeof(pPager->dbFileVers));
}
}
PAGER_INCR(sqlite3_pager_readdb_count);
PAGER_INCR(pPager->nRead);
IOTRACE(("PGIN %p %d\n", pPager, pPg->pgno));
PAGERTRACE(("FETCH %d page %d hash(%08x)\n",
PAGERID(pPager), pPg->pgno, pager_pagehash(pPg)));
return rc;
}
/*
** Update the value of the change-counter at offsets 24 and 92 in
** the header and the sqlite version number at offset 96.
**
** This is an unconditional update. See also the pager_incr_changecounter()
** routine which only updates the change-counter if the update is actually
** needed, as determined by the pPager->changeCountDone state variable.
*/
static void pager_write_changecounter(PgHdr *pPg){
u32 change_counter;
if( NEVER(pPg==0) ) return;
/* Increment the value just read and write it back to byte 24. */
change_counter = sqlite3Get4byte((u8*)pPg->pPager->dbFileVers)+1;
put32bits(((char*)pPg->pData)+24, change_counter);
/* Also store the SQLite version number in bytes 96..99 and in
** bytes 92..95 store the change counter for which the version number
** is valid. */
put32bits(((char*)pPg->pData)+92, change_counter);
put32bits(((char*)pPg->pData)+96, SQLITE_VERSION_NUMBER);
}
#ifndef SQLITE_OMIT_WAL
/*
** This function is invoked once for each page that has already been
** written into the log file when a WAL transaction is rolled back.
** Parameter iPg is the page number of said page. The pCtx argument
** is actually a pointer to the Pager structure.
**
** If page iPg is present in the cache, and has no outstanding references,
** it is discarded. Otherwise, if there are one or more outstanding
** references, the page content is reloaded from the database. If the
** attempt to reload content from the database is required and fails,
** return an SQLite error code. Otherwise, SQLITE_OK.
*/
static int pagerUndoCallback(void *pCtx, Pgno iPg){
int rc = SQLITE_OK;
Pager *pPager = (Pager *)pCtx;
PgHdr *pPg;
assert( pagerUseWal(pPager) );
pPg = sqlite3PagerLookup(pPager, iPg);
if( pPg ){
if( sqlite3PcachePageRefcount(pPg)==1 ){
sqlite3PcacheDrop(pPg);
}else{
rc = readDbPage(pPg);
if( rc==SQLITE_OK ){
pPager->xReiniter(pPg);
}
sqlite3PagerUnrefNotNull(pPg);
}
}
/* Normally, if a transaction is rolled back, any backup processes are
** updated as data is copied out of the rollback journal and into the
** database. This is not generally possible with a WAL database, as
** rollback involves simply truncating the log file. Therefore, if one
** or more frames have already been written to the log (and therefore
** also copied into the backup databases) as part of this transaction,
** the backups must be restarted.
*/
sqlite3BackupRestart(pPager->pBackup);
return rc;
}
/*
** This function is called to rollback a transaction on a WAL database.
*/
static int pagerRollbackWal(Pager *pPager){
int rc; /* Return Code */
PgHdr *pList; /* List of dirty pages to revert */
/* For all pages in the cache that are currently dirty or have already
** been written (but not committed) to the log file, do one of the
** following:
**
** + Discard the cached page (if refcount==0), or
** + Reload page content from the database (if refcount>0).
*/
pPager->dbSize = pPager->dbOrigSize;
rc = sqlite3WalUndo(pPager->pWal, pagerUndoCallback, (void *)pPager);
pList = sqlite3PcacheDirtyList(pPager->pPCache);
while( pList && rc==SQLITE_OK ){
PgHdr *pNext = pList->pDirty;
rc = pagerUndoCallback((void *)pPager, pList->pgno);
pList = pNext;
}
return rc;
}
/*
** This function is a wrapper around sqlite3WalFrames(). As well as logging
** the contents of the list of pages headed by pList (connected by pDirty),
** this function notifies any active backup processes that the pages have
** changed.
**
** The list of pages passed into this routine is always sorted by page number.
** Hence, if page 1 appears anywhere on the list, it will be the first page.
*/
static int pagerWalFrames(
Pager *pPager, /* Pager object */
PgHdr *pList, /* List of frames to log */
Pgno nTruncate, /* Database size after this commit */
int isCommit /* True if this is a commit */
){
int rc; /* Return code */
int nList; /* Number of pages in pList */
PgHdr *p; /* For looping over pages */
assert( pPager->pWal );
assert( pList );
#ifdef SQLITE_DEBUG
/* Verify that the page list is in ascending order */
for(p=pList; p && p->pDirty; p=p->pDirty){
assert( p->pgno < p->pDirty->pgno );
}
#endif
assert( pList->pDirty==0 || isCommit );
if( isCommit ){
/* If a WAL transaction is being committed, there is no point in writing
** any pages with page numbers greater than nTruncate into the WAL file.
** They will never be read by any client. So remove them from the pDirty
** list here. */
PgHdr **ppNext = &pList;
nList = 0;
for(p=pList; (*ppNext = p)!=0; p=p->pDirty){
if( p->pgno<=nTruncate ){
ppNext = &p->pDirty;
nList++;
}
}
assert( pList );
}else{
nList = 1;
}
pPager->aStat[PAGER_STAT_WRITE] += nList;
if( pList->pgno==1 ) pager_write_changecounter(pList);
rc = sqlite3WalFrames(pPager->pWal,
pPager->pageSize, pList, nTruncate, isCommit, pPager->walSyncFlags
);
if( rc==SQLITE_OK && pPager->pBackup ){
for(p=pList; p; p=p->pDirty){
sqlite3BackupUpdate(pPager->pBackup, p->pgno, (u8 *)p->pData);
}
}
#ifdef SQLITE_CHECK_PAGES
pList = sqlite3PcacheDirtyList(pPager->pPCache);
for(p=pList; p; p=p->pDirty){
pager_set_pagehash(p);
}
#endif
return rc;
}
/*
** Begin a read transaction on the WAL.
**
** This routine used to be called "pagerOpenSnapshot()" because it essentially
** makes a snapshot of the database at the current point in time and preserves
** that snapshot for use by the reader in spite of concurrently changes by
** other writers or checkpointers.
*/
static int pagerBeginReadTransaction(Pager *pPager){
int rc; /* Return code */
int changed = 0; /* True if cache must be reset */
assert( pagerUseWal(pPager) );
assert( pPager->eState==PAGER_OPEN || pPager->eState==PAGER_READER );
/* sqlite3WalEndReadTransaction() was not called for the previous
** transaction in locking_mode=EXCLUSIVE. So call it now. If we
** are in locking_mode=NORMAL and EndRead() was previously called,
** the duplicate call is harmless.
*/
sqlite3WalEndReadTransaction(pPager->pWal);
rc = sqlite3WalBeginReadTransaction(pPager->pWal, &changed);
if( rc!=SQLITE_OK || changed ){
pager_reset(pPager);
if( USEFETCH(pPager) ) sqlite3OsUnfetch(pPager->fd, 0, 0);
}
return rc;
}
#endif
/*
** This function is called as part of the transition from PAGER_OPEN
** to PAGER_READER state to determine the size of the database file
** in pages (assuming the page size currently stored in Pager.pageSize).
**
** If no error occurs, SQLITE_OK is returned and the size of the database
** in pages is stored in *pnPage. Otherwise, an error code (perhaps
** SQLITE_IOERR_FSTAT) is returned and *pnPage is left unmodified.
*/
static int pagerPagecount(Pager *pPager, Pgno *pnPage){
Pgno nPage; /* Value to return via *pnPage */
/* Query the WAL sub-system for the database size. The WalDbsize()
** function returns zero if the WAL is not open (i.e. Pager.pWal==0), or
** if the database size is not available. The database size is not
** available from the WAL sub-system if the log file is empty or
** contains no valid committed transactions.
*/
assert( pPager->eState==PAGER_OPEN );
assert( pPager->eLock>=SHARED_LOCK );
assert( isOpen(pPager->fd) );
assert( pPager->tempFile==0 );
nPage = sqlite3WalDbsize(pPager->pWal);
/* If the number of pages in the database is not available from the
** WAL sub-system, determine the page count based on the size of
** the database file. If the size of the database file is not an
** integer multiple of the page-size, round up the result.
*/
if( nPage==0 && ALWAYS(isOpen(pPager->fd)) ){
i64 n = 0; /* Size of db file in bytes */
int rc = sqlite3OsFileSize(pPager->fd, &n);
if( rc!=SQLITE_OK ){
return rc;
}
nPage = (Pgno)((n+pPager->pageSize-1) / pPager->pageSize);
}
/* If the current number of pages in the file is greater than the
** configured maximum pager number, increase the allowed limit so
** that the file can be read.
*/
if( nPage>pPager->mxPgno ){
pPager->mxPgno = (Pgno)nPage;
}
*pnPage = nPage;
return SQLITE_OK;
}
#ifndef SQLITE_OMIT_WAL
/*
** Check if the *-wal file that corresponds to the database opened by pPager
** exists if the database is not empty, or verify that the *-wal file does
** not exist (by deleting it) if the database file is empty.
**
** If the database is not empty and the *-wal file exists, open the pager
** in WAL mode. If the database is empty or if no *-wal file exists and
** if no error occurs, make sure Pager.journalMode is not set to
** PAGER_JOURNALMODE_WAL.
**
** Return SQLITE_OK or an error code.
**
** The caller must hold a SHARED lock on the database file to call this
** function. Because an EXCLUSIVE lock on the db file is required to delete
** a WAL on a none-empty database, this ensures there is no race condition
** between the xAccess() below and an xDelete() being executed by some
** other connection.
*/
static int pagerOpenWalIfPresent(Pager *pPager){
int rc = SQLITE_OK;
assert( pPager->eState==PAGER_OPEN );
assert( pPager->eLock>=SHARED_LOCK );
if( !pPager->tempFile ){
int isWal; /* True if WAL file exists */
rc = sqlite3OsAccess(
pPager->pVfs, pPager->zWal, SQLITE_ACCESS_EXISTS, &isWal
);
if( rc==SQLITE_OK ){
if( isWal ){
Pgno nPage; /* Size of the database file */
rc = pagerPagecount(pPager, &nPage);
if( rc ) return rc;
if( nPage==0 ){
rc = sqlite3OsDelete(pPager->pVfs, pPager->zWal, 0);
}else{
testcase( sqlite3PcachePagecount(pPager->pPCache)==0 );
rc = sqlite3PagerOpenWal(pPager, 0);
}
}else if( pPager->journalMode==PAGER_JOURNALMODE_WAL ){
pPager->journalMode = PAGER_JOURNALMODE_DELETE;
}
}
}
return rc;
}
#endif
/*
** Playback savepoint pSavepoint. Or, if pSavepoint==NULL, then playback
** the entire super-journal file. The case pSavepoint==NULL occurs when
** a ROLLBACK TO command is invoked on a SAVEPOINT that is a transaction
** savepoint.
**
** When pSavepoint is not NULL (meaning a non-transaction savepoint is
** being rolled back), then the rollback consists of up to three stages,
** performed in the order specified:
**
** * Pages are played back from the main journal starting at byte
** offset PagerSavepoint.iOffset and continuing to
** PagerSavepoint.iHdrOffset, or to the end of the main journal
** file if PagerSavepoint.iHdrOffset is zero.
**
** * If PagerSavepoint.iHdrOffset is not zero, then pages are played
** back starting from the journal header immediately following
** PagerSavepoint.iHdrOffset to the end of the main journal file.
**
** * Pages are then played back from the sub-journal file, starting
** with the PagerSavepoint.iSubRec and continuing to the end of
** the journal file.
**
** Throughout the rollback process, each time a page is rolled back, the
** corresponding bit is set in a bitvec structure (variable pDone in the
** implementation below). This is used to ensure that a page is only
** rolled back the first time it is encountered in either journal.
**
** If pSavepoint is NULL, then pages are only played back from the main
** journal file. There is no need for a bitvec in this case.
**
** In either case, before playback commences the Pager.dbSize variable
** is reset to the value that it held at the start of the savepoint
** (or transaction). No page with a page-number greater than this value
** is played back. If one is encountered it is simply skipped.
*/
static int pagerPlaybackSavepoint(Pager *pPager, PagerSavepoint *pSavepoint){
i64 szJ; /* Effective size of the main journal */
i64 iHdrOff; /* End of first segment of main-journal records */
int rc = SQLITE_OK; /* Return code */
Bitvec *pDone = 0; /* Bitvec to ensure pages played back only once */
assert( pPager->eState!=PAGER_ERROR );
assert( pPager->eState>=PAGER_WRITER_LOCKED );
/* Allocate a bitvec to use to store the set of pages rolled back */
if( pSavepoint ){
pDone = sqlite3BitvecCreate(pSavepoint->nOrig);
if( !pDone ){
return SQLITE_NOMEM_BKPT;
}
}
/* Set the database size back to the value it was before the savepoint
** being reverted was opened.
*/
pPager->dbSize = pSavepoint ? pSavepoint->nOrig : pPager->dbOrigSize;
pPager->changeCountDone = pPager->tempFile;
if( !pSavepoint && pagerUseWal(pPager) ){
return pagerRollbackWal(pPager);
}
/* Use pPager->journalOff as the effective size of the main rollback
** journal. The actual file might be larger than this in
** PAGER_JOURNALMODE_TRUNCATE or PAGER_JOURNALMODE_PERSIST. But anything
** past pPager->journalOff is off-limits to us.
*/
szJ = pPager->journalOff;
assert( pagerUseWal(pPager)==0 || szJ==0 );
/* Begin by rolling back records from the main journal starting at
** PagerSavepoint.iOffset and continuing to the next journal header.
** There might be records in the main journal that have a page number
** greater than the current database size (pPager->dbSize) but those
** will be skipped automatically. Pages are added to pDone as they
** are played back.
*/
if( pSavepoint && !pagerUseWal(pPager) ){
iHdrOff = pSavepoint->iHdrOffset ? pSavepoint->iHdrOffset : szJ;
pPager->journalOff = pSavepoint->iOffset;
while( rc==SQLITE_OK && pPager->journalOff<iHdrOff ){
rc = pager_playback_one_page(pPager, &pPager->journalOff, pDone, 1, 1);
}
assert( rc!=SQLITE_DONE );
}else{
pPager->journalOff = 0;
}
/* Continue rolling back records out of the main journal starting at
** the first journal header seen and continuing until the effective end
** of the main journal file. Continue to skip out-of-range pages and
** continue adding pages rolled back to pDone.
*/
while( rc==SQLITE_OK && pPager->journalOff<szJ ){
u32 ii; /* Loop counter */
u32 nJRec = 0; /* Number of Journal Records */
u32 dummy;
rc = readJournalHdr(pPager, 0, szJ, &nJRec, &dummy);
assert( rc!=SQLITE_DONE );
/*
** The "pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff"
** test is related to ticket #2565. See the discussion in the
** pager_playback() function for additional information.
*/
if( nJRec==0
&& pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff
){
nJRec = (u32)((szJ - pPager->journalOff)/JOURNAL_PG_SZ(pPager));
}
for(ii=0; rc==SQLITE_OK && ii<nJRec && pPager->journalOff<szJ; ii++){
rc = pager_playback_one_page(pPager, &pPager->journalOff, pDone, 1, 1);
}
assert( rc!=SQLITE_DONE );
}
assert( rc!=SQLITE_OK || pPager->journalOff>=szJ );
/* Finally, rollback pages from the sub-journal. Page that were
** previously rolled back out of the main journal (and are hence in pDone)
** will be skipped. Out-of-range pages are also skipped.
*/
if( pSavepoint ){
u32 ii; /* Loop counter */
i64 offset = (i64)pSavepoint->iSubRec*(4+pPager->pageSize);
if( pagerUseWal(pPager) ){
rc = sqlite3WalSavepointUndo(pPager->pWal, pSavepoint->aWalData);
}
for(ii=pSavepoint->iSubRec; rc==SQLITE_OK && ii<pPager->nSubRec; ii++){
assert( offset==(i64)ii*(4+pPager->pageSize) );
rc = pager_playback_one_page(pPager, &offset, pDone, 0, 1);
}
assert( rc!=SQLITE_DONE );
}
sqlite3BitvecDestroy(pDone);
if( rc==SQLITE_OK ){
pPager->journalOff = szJ;
}
return rc;
}
/*
** Change the maximum number of in-memory pages that are allowed
** before attempting to recycle clean and unused pages.
*/
void sqlite3PagerSetCachesize(Pager *pPager, int mxPage){
sqlite3PcacheSetCachesize(pPager->pPCache, mxPage);
}
/*
** Change the maximum number of in-memory pages that are allowed
** before attempting to spill pages to journal.
*/
int sqlite3PagerSetSpillsize(Pager *pPager, int mxPage){
return sqlite3PcacheSetSpillsize(pPager->pPCache, mxPage);
}
/*
** Invoke SQLITE_FCNTL_MMAP_SIZE based on the current value of szMmap.
*/
static void pagerFixMaplimit(Pager *pPager){
#if SQLITE_MAX_MMAP_SIZE>0
sqlite3_file *fd = pPager->fd;
if( isOpen(fd) && fd->pMethods->iVersion>=3 ){
sqlite3_int64 sz;
sz = pPager->szMmap;
pPager->bUseFetch = (sz>0);
setGetterMethod(pPager);
sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_MMAP_SIZE, &sz);
}
#endif
}
/*
** Change the maximum size of any memory mapping made of the database file.
*/
void sqlite3PagerSetMmapLimit(Pager *pPager, sqlite3_int64 szMmap){
pPager->szMmap = szMmap;
pagerFixMaplimit(pPager);
}
/*
** Free as much memory as possible from the pager.
*/
void sqlite3PagerShrink(Pager *pPager){
sqlite3PcacheShrink(pPager->pPCache);
}
/*
** Adjust settings of the pager to those specified in the pgFlags parameter.
**
** The "level" in pgFlags & PAGER_SYNCHRONOUS_MASK sets the robustness
** of the database to damage due to OS crashes or power failures by
** changing the number of syncs()s when writing the journals.
** There are four levels:
**
** OFF sqlite3OsSync() is never called. This is the default
** for temporary and transient files.
**
** NORMAL The journal is synced once before writes begin on the
** database. This is normally adequate protection, but
** it is theoretically possible, though very unlikely,
** that an inopertune power failure could leave the journal
** in a state which would cause damage to the database
** when it is rolled back.
**
** FULL The journal is synced twice before writes begin on the
** database (with some additional information - the nRec field
** of the journal header - being written in between the two
** syncs). If we assume that writing a
** single disk sector is atomic, then this mode provides
** assurance that the journal will not be corrupted to the
** point of causing damage to the database during rollback.
**
** EXTRA This is like FULL except that is also syncs the directory
** that contains the rollback journal after the rollback
** journal is unlinked.
**
** The above is for a rollback-journal mode. For WAL mode, OFF continues
** to mean that no syncs ever occur. NORMAL means that the WAL is synced
** prior to the start of checkpoint and that the database file is synced
** at the conclusion of the checkpoint if the entire content of the WAL
** was written back into the database. But no sync operations occur for
** an ordinary commit in NORMAL mode with WAL. FULL means that the WAL
** file is synced following each commit operation, in addition to the
** syncs associated with NORMAL. There is no difference between FULL
** and EXTRA for WAL mode.
**
** Do not confuse synchronous=FULL with SQLITE_SYNC_FULL. The
** SQLITE_SYNC_FULL macro means to use the MacOSX-style full-fsync
** using fcntl(F_FULLFSYNC). SQLITE_SYNC_NORMAL means to do an
** ordinary fsync() call. There is no difference between SQLITE_SYNC_FULL
** and SQLITE_SYNC_NORMAL on platforms other than MacOSX. But the
** synchronous=FULL versus synchronous=NORMAL setting determines when
** the xSync primitive is called and is relevant to all platforms.
**
** Numeric values associated with these states are OFF==1, NORMAL=2,
** and FULL=3.
*/
void sqlite3PagerSetFlags(
Pager *pPager, /* The pager to set safety level for */
unsigned pgFlags /* Various flags */
){
unsigned level = pgFlags & PAGER_SYNCHRONOUS_MASK;
if( pPager->tempFile ){
pPager->noSync = 1;
pPager->fullSync = 0;
pPager->extraSync = 0;
}else{
pPager->noSync = level==PAGER_SYNCHRONOUS_OFF ?1:0;
pPager->fullSync = level>=PAGER_SYNCHRONOUS_FULL ?1:0;
pPager->extraSync = level==PAGER_SYNCHRONOUS_EXTRA ?1:0;
}
if( pPager->noSync ){
pPager->syncFlags = 0;
}else if( pgFlags & PAGER_FULLFSYNC ){
pPager->syncFlags = SQLITE_SYNC_FULL;
}else{
pPager->syncFlags = SQLITE_SYNC_NORMAL;
}
pPager->walSyncFlags = (pPager->syncFlags<<2);
if( pPager->fullSync ){
pPager->walSyncFlags |= pPager->syncFlags;
}
if( (pgFlags & PAGER_CKPT_FULLFSYNC) && !pPager->noSync ){
pPager->walSyncFlags |= (SQLITE_SYNC_FULL<<2);
}
if( pgFlags & PAGER_CACHESPILL ){
pPager->doNotSpill &= ~SPILLFLAG_OFF;
}else{
pPager->doNotSpill |= SPILLFLAG_OFF;
}
}
/*
** The following global variable is incremented whenever the library
** attempts to open a temporary file. This information is used for
** testing and analysis only.
*/
#ifdef SQLITE_TEST
int sqlite3_opentemp_count = 0;
#endif
/*
** Open a temporary file.
**
** Write the file descriptor into *pFile. Return SQLITE_OK on success
** or some other error code if we fail. The OS will automatically
** delete the temporary file when it is closed.
**
** The flags passed to the VFS layer xOpen() call are those specified
** by parameter vfsFlags ORed with the following:
**
** SQLITE_OPEN_READWRITE
** SQLITE_OPEN_CREATE
** SQLITE_OPEN_EXCLUSIVE
** SQLITE_OPEN_DELETEONCLOSE
*/
static int pagerOpentemp(
Pager *pPager, /* The pager object */
sqlite3_file *pFile, /* Write the file descriptor here */
int vfsFlags /* Flags passed through to the VFS */
){
int rc; /* Return code */
#ifdef SQLITE_TEST
sqlite3_opentemp_count++; /* Used for testing and analysis only */
#endif
vfsFlags |= SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE |
SQLITE_OPEN_EXCLUSIVE | SQLITE_OPEN_DELETEONCLOSE;
rc = sqlite3OsOpen(pPager->pVfs, 0, pFile, vfsFlags, 0);
assert( rc!=SQLITE_OK || isOpen(pFile) );
return rc;
}
/*
** Set the busy handler function.
**
** The pager invokes the busy-handler if sqlite3OsLock() returns
** SQLITE_BUSY when trying to upgrade from no-lock to a SHARED lock,
** or when trying to upgrade from a RESERVED lock to an EXCLUSIVE
** lock. It does *not* invoke the busy handler when upgrading from
** SHARED to RESERVED, or when upgrading from SHARED to EXCLUSIVE
** (which occurs during hot-journal rollback). Summary:
**
** Transition | Invokes xBusyHandler
** --------------------------------------------------------
** NO_LOCK -> SHARED_LOCK | Yes
** SHARED_LOCK -> RESERVED_LOCK | No
** SHARED_LOCK -> EXCLUSIVE_LOCK | No
** RESERVED_LOCK -> EXCLUSIVE_LOCK | Yes
**
** If the busy-handler callback returns non-zero, the lock is
** retried. If it returns zero, then the SQLITE_BUSY error is
** returned to the caller of the pager API function.
*/
void sqlite3PagerSetBusyHandler(
Pager *pPager, /* Pager object */
int (*xBusyHandler)(void *), /* Pointer to busy-handler function */
void *pBusyHandlerArg /* Argument to pass to xBusyHandler */
){
void **ap;
pPager->xBusyHandler = xBusyHandler;
pPager->pBusyHandlerArg = pBusyHandlerArg;
ap = (void **)&pPager->xBusyHandler;
assert( ((int(*)(void *))(ap[0]))==xBusyHandler );
assert( ap[1]==pBusyHandlerArg );
sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_BUSYHANDLER, (void *)ap);
}
/*
** Change the page size used by the Pager object. The new page size
** is passed in *pPageSize.
**
** If the pager is in the error state when this function is called, it
** is a no-op. The value returned is the error state error code (i.e.
** one of SQLITE_IOERR, an SQLITE_IOERR_xxx sub-code or SQLITE_FULL).
**
** Otherwise, if all of the following are true:
**
** * the new page size (value of *pPageSize) is valid (a power
** of two between 512 and SQLITE_MAX_PAGE_SIZE, inclusive), and
**
** * there are no outstanding page references, and
**
** * the database is either not an in-memory database or it is
** an in-memory database that currently consists of zero pages.
**
** then the pager object page size is set to *pPageSize.
**
** If the page size is changed, then this function uses sqlite3PagerMalloc()
** to obtain a new Pager.pTmpSpace buffer. If this allocation attempt
** fails, SQLITE_NOMEM is returned and the page size remains unchanged.
** In all other cases, SQLITE_OK is returned.
**
** If the page size is not changed, either because one of the enumerated
** conditions above is not true, the pager was in error state when this
** function was called, or because the memory allocation attempt failed,
** then *pPageSize is set to the old, retained page size before returning.
*/
int sqlite3PagerSetPagesize(Pager *pPager, u32 *pPageSize, int nReserve){
int rc = SQLITE_OK;
/* It is not possible to do a full assert_pager_state() here, as this
** function may be called from within PagerOpen(), before the state
** of the Pager object is internally consistent.
**
** At one point this function returned an error if the pager was in
** PAGER_ERROR state. But since PAGER_ERROR state guarantees that
** there is at least one outstanding page reference, this function
** is a no-op for that case anyhow.
*/
u32 pageSize = *pPageSize;
assert( pageSize==0 || (pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE) );
if( (pPager->memDb==0 || pPager->dbSize==0)
&& sqlite3PcacheRefCount(pPager->pPCache)==0
&& pageSize && pageSize!=(u32)pPager->pageSize
){
char *pNew = NULL; /* New temp space */
i64 nByte = 0;
if( pPager->eState>PAGER_OPEN && isOpen(pPager->fd) ){
rc = sqlite3OsFileSize(pPager->fd, &nByte);
}
if( rc==SQLITE_OK ){
/* 8 bytes of zeroed overrun space is sufficient so that the b-tree
* cell header parser will never run off the end of the allocation */
pNew = (char *)sqlite3PageMalloc(pageSize+8);
if( !pNew ){
rc = SQLITE_NOMEM_BKPT;
}else{
memset(pNew+pageSize, 0, 8);
}
}
if( rc==SQLITE_OK ){
pager_reset(pPager);
rc = sqlite3PcacheSetPageSize(pPager->pPCache, pageSize);
}
if( rc==SQLITE_OK ){
sqlite3PageFree(pPager->pTmpSpace);
pPager->pTmpSpace = pNew;
pPager->dbSize = (Pgno)((nByte+pageSize-1)/pageSize);
pPager->pageSize = pageSize;
pPager->lckPgno = (Pgno)(PENDING_BYTE/pageSize) + 1;
}else{
sqlite3PageFree(pNew);
}
}
*pPageSize = pPager->pageSize;
if( rc==SQLITE_OK ){
if( nReserve<0 ) nReserve = pPager->nReserve;
assert( nReserve>=0 && nReserve<1000 );
pPager->nReserve = (i16)nReserve;
pagerFixMaplimit(pPager);
}
return rc;
}
/*
** Return a pointer to the "temporary page" buffer held internally
** by the pager. This is a buffer that is big enough to hold the
** entire content of a database page. This buffer is used internally
** during rollback and will be overwritten whenever a rollback
** occurs. But other modules are free to use it too, as long as
** no rollbacks are happening.
*/
void *sqlite3PagerTempSpace(Pager *pPager){
return pPager->pTmpSpace;
}
/*
** Attempt to set the maximum database page count if mxPage is positive.
** Make no changes if mxPage is zero or negative. And never reduce the
** maximum page count below the current size of the database.
**
** Regardless of mxPage, return the current maximum page count.
*/
Pgno sqlite3PagerMaxPageCount(Pager *pPager, Pgno mxPage){
if( mxPage>0 ){
pPager->mxPgno = mxPage;
}
assert( pPager->eState!=PAGER_OPEN ); /* Called only by OP_MaxPgcnt */
/* assert( pPager->mxPgno>=pPager->dbSize ); */
/* OP_MaxPgcnt ensures that the parameter passed to this function is not
** less than the total number of valid pages in the database. But this
** may be less than Pager.dbSize, and so the assert() above is not valid */
return pPager->mxPgno;
}
/*
** The following set of routines are used to disable the simulated
** I/O error mechanism. These routines are used to avoid simulated
** errors in places where we do not care about errors.
**
** Unless -DSQLITE_TEST=1 is used, these routines are all no-ops
** and generate no code.
*/
#ifdef SQLITE_TEST
extern int sqlite3_io_error_pending;
extern int sqlite3_io_error_hit;
static int saved_cnt;
void disable_simulated_io_errors(void){
saved_cnt = sqlite3_io_error_pending;
sqlite3_io_error_pending = -1;
}
void enable_simulated_io_errors(void){
sqlite3_io_error_pending = saved_cnt;
}
#else
# define disable_simulated_io_errors()
# define enable_simulated_io_errors()
#endif
/*
** Read the first N bytes from the beginning of the file into memory
** that pDest points to.
**
** If the pager was opened on a transient file (zFilename==""), or
** opened on a file less than N bytes in size, the output buffer is
** zeroed and SQLITE_OK returned. The rationale for this is that this
** function is used to read database headers, and a new transient or
** zero sized database has a header than consists entirely of zeroes.
**
** If any IO error apart from SQLITE_IOERR_SHORT_READ is encountered,
** the error code is returned to the caller and the contents of the
** output buffer undefined.
*/
int sqlite3PagerReadFileheader(Pager *pPager, int N, unsigned char *pDest){
int rc = SQLITE_OK;
memset(pDest, 0, N);
assert( isOpen(pPager->fd) || pPager->tempFile );
/* This routine is only called by btree immediately after creating
** the Pager object. There has not been an opportunity to transition
** to WAL mode yet.
*/
assert( !pagerUseWal(pPager) );
if( isOpen(pPager->fd) ){
IOTRACE(("DBHDR %p 0 %d\n", pPager, N))
rc = sqlite3OsRead(pPager->fd, pDest, N, 0);
if( rc==SQLITE_IOERR_SHORT_READ ){
rc = SQLITE_OK;
}
}
return rc;
}
/*
** This function may only be called when a read-transaction is open on
** the pager. It returns the total number of pages in the database.
**
** However, if the file is between 1 and <page-size> bytes in size, then
** this is considered a 1 page file.
*/
void sqlite3PagerPagecount(Pager *pPager, int *pnPage){
assert( pPager->eState>=PAGER_READER );
assert( pPager->eState!=PAGER_WRITER_FINISHED );
*pnPage = (int)pPager->dbSize;
}
/*
** Try to obtain a lock of type locktype on the database file. If
** a similar or greater lock is already held, this function is a no-op
** (returning SQLITE_OK immediately).
**
** Otherwise, attempt to obtain the lock using sqlite3OsLock(). Invoke
** the busy callback if the lock is currently not available. Repeat
** until the busy callback returns false or until the attempt to
** obtain the lock succeeds.
**
** Return SQLITE_OK on success and an error code if we cannot obtain
** the lock. If the lock is obtained successfully, set the Pager.state
** variable to locktype before returning.
*/
static int pager_wait_on_lock(Pager *pPager, int locktype){
int rc; /* Return code */
/* Check that this is either a no-op (because the requested lock is
** already held), or one of the transitions that the busy-handler
** may be invoked during, according to the comment above
** sqlite3PagerSetBusyhandler().
*/
assert( (pPager->eLock>=locktype)
|| (pPager->eLock==NO_LOCK && locktype==SHARED_LOCK)
|| (pPager->eLock==RESERVED_LOCK && locktype==EXCLUSIVE_LOCK)
);
do {
rc = pagerLockDb(pPager, locktype);
}while( rc==SQLITE_BUSY && pPager->xBusyHandler(pPager->pBusyHandlerArg) );
return rc;
}
/*
** Function assertTruncateConstraint(pPager) checks that one of the
** following is true for all dirty pages currently in the page-cache:
**
** a) The page number is less than or equal to the size of the
** current database image, in pages, OR
**
** b) if the page content were written at this time, it would not
** be necessary to write the current content out to the sub-journal.
**
** If the condition asserted by this function were not true, and the
** dirty page were to be discarded from the cache via the pagerStress()
** routine, pagerStress() would not write the current page content to
** the database file. If a savepoint transaction were rolled back after
** this happened, the correct behavior would be to restore the current
** content of the page. However, since this content is not present in either
** the database file or the portion of the rollback journal and
** sub-journal rolled back the content could not be restored and the
** database image would become corrupt. It is therefore fortunate that
** this circumstance cannot arise.
*/
#if defined(SQLITE_DEBUG)
static void assertTruncateConstraintCb(PgHdr *pPg){
Pager *pPager = pPg->pPager;
assert( pPg->flags&PGHDR_DIRTY );
if( pPg->pgno>pPager->dbSize ){ /* if (a) is false */
Pgno pgno = pPg->pgno;
int i;
for(i=0; i<pPg->pPager->nSavepoint; i++){
PagerSavepoint *p = &pPager->aSavepoint[i];
assert( p->nOrig<pgno || sqlite3BitvecTestNotNull(p->pInSavepoint,pgno) );
}
}
}
static void assertTruncateConstraint(Pager *pPager){
sqlite3PcacheIterateDirty(pPager->pPCache, assertTruncateConstraintCb);
}
#else
# define assertTruncateConstraint(pPager)
#endif
/*
** Truncate the in-memory database file image to nPage pages. This
** function does not actually modify the database file on disk. It
** just sets the internal state of the pager object so that the
** truncation will be done when the current transaction is committed.
**
** This function is only called right before committing a transaction.
** Once this function has been called, the transaction must either be
** rolled back or committed. It is not safe to call this function and
** then continue writing to the database.
*/
void sqlite3PagerTruncateImage(Pager *pPager, Pgno nPage){
assert( pPager->dbSize>=nPage || CORRUPT_DB );
assert( pPager->eState>=PAGER_WRITER_CACHEMOD );
pPager->dbSize = nPage;
/* At one point the code here called assertTruncateConstraint() to
** ensure that all pages being truncated away by this operation are,
** if one or more savepoints are open, present in the savepoint
** journal so that they can be restored if the savepoint is rolled
** back. This is no longer necessary as this function is now only
** called right before committing a transaction. So although the
** Pager object may still have open savepoints (Pager.nSavepoint!=0),
** they cannot be rolled back. So the assertTruncateConstraint() call
** is no longer correct. */
}
/*
** This function is called before attempting a hot-journal rollback. It
** syncs the journal file to disk, then sets pPager->journalHdr to the
** size of the journal file so that the pager_playback() routine knows
** that the entire journal file has been synced.
**
** Syncing a hot-journal to disk before attempting to roll it back ensures
** that if a power-failure occurs during the rollback, the process that
** attempts rollback following system recovery sees the same journal
** content as this process.
**
** If everything goes as planned, SQLITE_OK is returned. Otherwise,
** an SQLite error code.
*/
static int pagerSyncHotJournal(Pager *pPager){
int rc = SQLITE_OK;
if( !pPager->noSync ){
rc = sqlite3OsSync(pPager->jfd, SQLITE_SYNC_NORMAL);
}
if( rc==SQLITE_OK ){
rc = sqlite3OsFileSize(pPager->jfd, &pPager->journalHdr);
}
return rc;
}
#if SQLITE_MAX_MMAP_SIZE>0
/*
** Obtain a reference to a memory mapped page object for page number pgno.
** The new object will use the pointer pData, obtained from xFetch().
** If successful, set *ppPage to point to the new page reference
** and return SQLITE_OK. Otherwise, return an SQLite error code and set
** *ppPage to zero.
**
** Page references obtained by calling this function should be released
** by calling pagerReleaseMapPage().
*/
static int pagerAcquireMapPage(
Pager *pPager, /* Pager object */
Pgno pgno, /* Page number */
void *pData, /* xFetch()'d data for this page */
PgHdr **ppPage /* OUT: Acquired page object */
){
PgHdr *p; /* Memory mapped page to return */
if( pPager->pMmapFreelist ){
*ppPage = p = pPager->pMmapFreelist;
pPager->pMmapFreelist = p->pDirty;
p->pDirty = 0;
assert( pPager->nExtra>=8 );
memset(p->pExtra, 0, 8);
}else{
*ppPage = p = (PgHdr *)sqlite3MallocZero(sizeof(PgHdr) + pPager->nExtra);
if( p==0 ){
sqlite3OsUnfetch(pPager->fd, (i64)(pgno-1) * pPager->pageSize, pData);
return SQLITE_NOMEM_BKPT;
}
p->pExtra = (void *)&p[1];
assert( EIGHT_BYTE_ALIGNMENT( p->pExtra ) );
p->flags = PGHDR_MMAP;
p->nRef = 1;
p->pPager = pPager;
}
assert( p->pExtra==(void *)&p[1] );
assert( p->pPage==0 );
assert( p->flags==PGHDR_MMAP );
assert( p->pPager==pPager );
assert( p->nRef==1 );
p->pgno = pgno;
p->pData = pData;
pPager->nMmapOut++;
return SQLITE_OK;
}
#endif
/*
** Release a reference to page pPg. pPg must have been returned by an
** earlier call to pagerAcquireMapPage().
*/
static void pagerReleaseMapPage(PgHdr *pPg){
Pager *pPager = pPg->pPager;
pPager->nMmapOut--;
pPg->pDirty = pPager->pMmapFreelist;
pPager->pMmapFreelist = pPg;
assert( pPager->fd->pMethods->iVersion>=3 );
sqlite3OsUnfetch(pPager->fd, (i64)(pPg->pgno-1)*pPager->pageSize, pPg->pData);
}
/*
** Free all PgHdr objects stored in the Pager.pMmapFreelist list.
*/
static void pagerFreeMapHdrs(Pager *pPager){
PgHdr *p;
PgHdr *pNext;
for(p=pPager->pMmapFreelist; p; p=pNext){
pNext = p->pDirty;
sqlite3_free(p);
}
}
/* Verify that the database file has not be deleted or renamed out from
** under the pager. Return SQLITE_OK if the database is still where it ought
** to be on disk. Return non-zero (SQLITE_READONLY_DBMOVED or some other error
** code from sqlite3OsAccess()) if the database has gone missing.
*/
static int databaseIsUnmoved(Pager *pPager){
int bHasMoved = 0;
int rc;
if( pPager->tempFile ) return SQLITE_OK;
if( pPager->dbSize==0 ) return SQLITE_OK;
assert( pPager->zFilename && pPager->zFilename[0] );
rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_HAS_MOVED, &bHasMoved);
if( rc==SQLITE_NOTFOUND ){
/* If the HAS_MOVED file-control is unimplemented, assume that the file
** has not been moved. That is the historical behavior of SQLite: prior to
** version 3.8.3, it never checked */
rc = SQLITE_OK;
}else if( rc==SQLITE_OK && bHasMoved ){
rc = SQLITE_READONLY_DBMOVED;
}
return rc;
}
/*
** Shutdown the page cache. Free all memory and close all files.
**
** If a transaction was in progress when this routine is called, that
** transaction is rolled back. All outstanding pages are invalidated
** and their memory is freed. Any attempt to use a page associated
** with this page cache after this function returns will likely
** result in a coredump.
**
** This function always succeeds. If a transaction is active an attempt
** is made to roll it back. If an error occurs during the rollback
** a hot journal may be left in the filesystem but no error is returned
** to the caller.
*/
int sqlite3PagerClose(Pager *pPager, sqlite3 *db){
u8 *pTmp = (u8*)pPager->pTmpSpace;
assert( db || pagerUseWal(pPager)==0 );
assert( assert_pager_state(pPager) );
disable_simulated_io_errors();
sqlite3BeginBenignMalloc();
pagerFreeMapHdrs(pPager);
/* pPager->errCode = 0; */
pPager->exclusiveMode = 0;
#ifndef SQLITE_OMIT_WAL
{
u8 *a = 0;
assert( db || pPager->pWal==0 );
if( db && 0==(db->flags & SQLITE_NoCkptOnClose)
&& SQLITE_OK==databaseIsUnmoved(pPager)
){
a = pTmp;
}
sqlite3WalClose(pPager->pWal, db, pPager->walSyncFlags, pPager->pageSize,a);
pPager->pWal = 0;
}
#endif
pager_reset(pPager);
if( MEMDB ){
pager_unlock(pPager);
}else{
/* If it is open, sync the journal file before calling UnlockAndRollback.
** If this is not done, then an unsynced portion of the open journal
** file may be played back into the database. If a power failure occurs
** while this is happening, the database could become corrupt.
**
** If an error occurs while trying to sync the journal, shift the pager
** into the ERROR state. This causes UnlockAndRollback to unlock the
** database and close the journal file without attempting to roll it
** back or finalize it. The next database user will have to do hot-journal
** rollback before accessing the database file.
*/
if( isOpen(pPager->jfd) ){
pager_error(pPager, pagerSyncHotJournal(pPager));
}
pagerUnlockAndRollback(pPager);
}
sqlite3EndBenignMalloc();
enable_simulated_io_errors();
PAGERTRACE(("CLOSE %d\n", PAGERID(pPager)));
IOTRACE(("CLOSE %p\n", pPager))
sqlite3OsClose(pPager->jfd);
sqlite3OsClose(pPager->fd);
sqlite3PageFree(pTmp);
sqlite3PcacheClose(pPager->pPCache);
assert( !pPager->aSavepoint && !pPager->pInJournal );
assert( !isOpen(pPager->jfd) && !isOpen(pPager->sjfd) );
sqlite3_free(pPager);
return SQLITE_OK;
}
#if !defined(NDEBUG) || defined(SQLITE_TEST)
/*
** Return the page number for page pPg.
*/
Pgno sqlite3PagerPagenumber(DbPage *pPg){
return pPg->pgno;
}
#endif
/*
** Increment the reference count for page pPg.
*/
void sqlite3PagerRef(DbPage *pPg){
sqlite3PcacheRef(pPg);
}
/*
** Sync the journal. In other words, make sure all the pages that have
** been written to the journal have actually reached the surface of the
** disk and can be restored in the event of a hot-journal rollback.
**
** If the Pager.noSync flag is set, then this function is a no-op.
** Otherwise, the actions required depend on the journal-mode and the
** device characteristics of the file-system, as follows:
**
** * If the journal file is an in-memory journal file, no action need
** be taken.
**
** * Otherwise, if the device does not support the SAFE_APPEND property,
** then the nRec field of the most recently written journal header
** is updated to contain the number of journal records that have
** been written following it. If the pager is operating in full-sync
** mode, then the journal file is synced before this field is updated.
**
** * If the device does not support the SEQUENTIAL property, then
** journal file is synced.
**
** Or, in pseudo-code:
**
** if( NOT <in-memory journal> ){
** if( NOT SAFE_APPEND ){
** if( <full-sync mode> ) xSync(<journal file>);
** <update nRec field>
** }
** if( NOT SEQUENTIAL ) xSync(<journal file>);
** }
**
** If successful, this routine clears the PGHDR_NEED_SYNC flag of every
** page currently held in memory before returning SQLITE_OK. If an IO
** error is encountered, then the IO error code is returned to the caller.
*/
static int syncJournal(Pager *pPager, int newHdr){
int rc; /* Return code */
assert( pPager->eState==PAGER_WRITER_CACHEMOD
|| pPager->eState==PAGER_WRITER_DBMOD
);
assert( assert_pager_state(pPager) );
assert( !pagerUseWal(pPager) );
rc = sqlite3PagerExclusiveLock(pPager);
if( rc!=SQLITE_OK ) return rc;
if( !pPager->noSync ){
assert( !pPager->tempFile );
if( isOpen(pPager->jfd) && pPager->journalMode!=PAGER_JOURNALMODE_MEMORY ){
const int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
assert( isOpen(pPager->jfd) );
if( 0==(iDc&SQLITE_IOCAP_SAFE_APPEND) ){
/* This block deals with an obscure problem. If the last connection
** that wrote to this database was operating in persistent-journal
** mode, then the journal file may at this point actually be larger
** than Pager.journalOff bytes. If the next thing in the journal
** file happens to be a journal-header (written as part of the
** previous connection's transaction), and a crash or power-failure
** occurs after nRec is updated but before this connection writes
** anything else to the journal file (or commits/rolls back its
** transaction), then SQLite may become confused when doing the
** hot-journal rollback following recovery. It may roll back all
** of this connections data, then proceed to rolling back the old,
** out-of-date data that follows it. Database corruption.
**
** To work around this, if the journal file does appear to contain
** a valid header following Pager.journalOff, then write a 0x00
** byte to the start of it to prevent it from being recognized.
**
** Variable iNextHdrOffset is set to the offset at which this
** problematic header will occur, if it exists. aMagic is used
** as a temporary buffer to inspect the first couple of bytes of
** the potential journal header.
*/
i64 iNextHdrOffset;
u8 aMagic[8];
u8 zHeader[sizeof(aJournalMagic)+4];
memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic));
put32bits(&zHeader[sizeof(aJournalMagic)], pPager->nRec);
iNextHdrOffset = journalHdrOffset(pPager);
rc = sqlite3OsRead(pPager->jfd, aMagic, 8, iNextHdrOffset);
if( rc==SQLITE_OK && 0==memcmp(aMagic, aJournalMagic, 8) ){
static const u8 zerobyte = 0;
rc = sqlite3OsWrite(pPager->jfd, &zerobyte, 1, iNextHdrOffset);
}
if( rc!=SQLITE_OK && rc!=SQLITE_IOERR_SHORT_READ ){
return rc;
}
/* Write the nRec value into the journal file header. If in
** full-synchronous mode, sync the journal first. This ensures that
** all data has really hit the disk before nRec is updated to mark
** it as a candidate for rollback.
**
** This is not required if the persistent media supports the
** SAFE_APPEND property. Because in this case it is not possible
** for garbage data to be appended to the file, the nRec field
** is populated with 0xFFFFFFFF when the journal header is written
** and never needs to be updated.
*/
if( pPager->fullSync && 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){
PAGERTRACE(("SYNC journal of %d\n", PAGERID(pPager)));
IOTRACE(("JSYNC %p\n", pPager))
rc = sqlite3OsSync(pPager->jfd, pPager->syncFlags);
if( rc!=SQLITE_OK ) return rc;
}
IOTRACE(("JHDR %p %lld\n", pPager, pPager->journalHdr));
rc = sqlite3OsWrite(
pPager->jfd, zHeader, sizeof(zHeader), pPager->journalHdr
);
if( rc!=SQLITE_OK ) return rc;
}
if( 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){
PAGERTRACE(("SYNC journal of %d\n", PAGERID(pPager)));
IOTRACE(("JSYNC %p\n", pPager))
rc = sqlite3OsSync(pPager->jfd, pPager->syncFlags|
(pPager->syncFlags==SQLITE_SYNC_FULL?SQLITE_SYNC_DATAONLY:0)
);
if( rc!=SQLITE_OK ) return rc;
}
pPager->journalHdr = pPager->journalOff;
if( newHdr && 0==(iDc&SQLITE_IOCAP_SAFE_APPEND) ){
pPager->nRec = 0;
rc = writeJournalHdr(pPager);
if( rc!=SQLITE_OK ) return rc;
}
}else{
pPager->journalHdr = pPager->journalOff;
}
}
/* Unless the pager is in noSync mode, the journal file was just
** successfully synced. Either way, clear the PGHDR_NEED_SYNC flag on
** all pages.
*/
sqlite3PcacheClearSyncFlags(pPager->pPCache);
pPager->eState = PAGER_WRITER_DBMOD;
assert( assert_pager_state(pPager) );
return SQLITE_OK;
}
/*
** The argument is the first in a linked list of dirty pages connected
** by the PgHdr.pDirty pointer. This function writes each one of the
** in-memory pages in the list to the database file. The argument may
** be NULL, representing an empty list. In this case this function is
** a no-op.
**
** The pager must hold at least a RESERVED lock when this function
** is called. Before writing anything to the database file, this lock
** is upgraded to an EXCLUSIVE lock. If the lock cannot be obtained,
** SQLITE_BUSY is returned and no data is written to the database file.
**
** If the pager is a temp-file pager and the actual file-system file
** is not yet open, it is created and opened before any data is
** written out.
**
** Once the lock has been upgraded and, if necessary, the file opened,
** the pages are written out to the database file in list order. Writing
** a page is skipped if it meets either of the following criteria:
**
** * The page number is greater than Pager.dbSize, or
** * The PGHDR_DONT_WRITE flag is set on the page.
**
** If writing out a page causes the database file to grow, Pager.dbFileSize
** is updated accordingly. If page 1 is written out, then the value cached
** in Pager.dbFileVers[] is updated to match the new value stored in
** the database file.
**
** If everything is successful, SQLITE_OK is returned. If an IO error
** occurs, an IO error code is returned. Or, if the EXCLUSIVE lock cannot
** be obtained, SQLITE_BUSY is returned.
*/
static int pager_write_pagelist(Pager *pPager, PgHdr *pList){
int rc = SQLITE_OK; /* Return code */
/* This function is only called for rollback pagers in WRITER_DBMOD state. */
assert( !pagerUseWal(pPager) );
assert( pPager->tempFile || pPager->eState==PAGER_WRITER_DBMOD );
assert( pPager->eLock==EXCLUSIVE_LOCK );
assert( isOpen(pPager->fd) || pList->pDirty==0 );
/* If the file is a temp-file has not yet been opened, open it now. It
** is not possible for rc to be other than SQLITE_OK if this branch
** is taken, as pager_wait_on_lock() is a no-op for temp-files.
*/
if( !isOpen(pPager->fd) ){
assert( pPager->tempFile && rc==SQLITE_OK );
rc = pagerOpentemp(pPager, pPager->fd, pPager->vfsFlags);
}
/* Before the first write, give the VFS a hint of what the final
** file size will be.
*/
assert( rc!=SQLITE_OK || isOpen(pPager->fd) );
if( rc==SQLITE_OK
&& pPager->dbHintSize<pPager->dbSize
&& (pList->pDirty || pList->pgno>pPager->dbHintSize)
){
sqlite3_int64 szFile = pPager->pageSize * (sqlite3_int64)pPager->dbSize;
sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_SIZE_HINT, &szFile);
pPager->dbHintSize = pPager->dbSize;
}
while( rc==SQLITE_OK && pList ){
Pgno pgno = pList->pgno;
/* If there are dirty pages in the page cache with page numbers greater
** than Pager.dbSize, this means sqlite3PagerTruncateImage() was called to
** make the file smaller (presumably by auto-vacuum code). Do not write
** any such pages to the file.
**
** Also, do not write out any page that has the PGHDR_DONT_WRITE flag
** set (set by sqlite3PagerDontWrite()).
*/
if( pgno<=pPager->dbSize && 0==(pList->flags&PGHDR_DONT_WRITE) ){
i64 offset = (pgno-1)*(i64)pPager->pageSize; /* Offset to write */
char *pData; /* Data to write */
assert( (pList->flags&PGHDR_NEED_SYNC)==0 );
if( pList->pgno==1 ) pager_write_changecounter(pList);
pData = pList->pData;
/* Write out the page data. */
rc = sqlite3OsWrite(pPager->fd, pData, pPager->pageSize, offset);
/* If page 1 was just written, update Pager.dbFileVers to match
** the value now stored in the database file. If writing this
** page caused the database file to grow, update dbFileSize.
*/
if( pgno==1 ){
memcpy(&pPager->dbFileVers, &pData[24], sizeof(pPager->dbFileVers));
}
if( pgno>pPager->dbFileSize ){
pPager->dbFileSize = pgno;
}
pPager->aStat[PAGER_STAT_WRITE]++;
/* Update any backup objects copying the contents of this pager. */
sqlite3BackupUpdate(pPager->pBackup, pgno, (u8*)pList->pData);
PAGERTRACE(("STORE %d page %d hash(%08x)\n",
PAGERID(pPager), pgno, pager_pagehash(pList)));
IOTRACE(("PGOUT %p %d\n", pPager, pgno));
PAGER_INCR(sqlite3_pager_writedb_count);
}else{
PAGERTRACE(("NOSTORE %d page %d\n", PAGERID(pPager), pgno));
}
pager_set_pagehash(pList);
pList = pList->pDirty;
}
return rc;
}
/*
** Ensure that the sub-journal file is open. If it is already open, this
** function is a no-op.
**
** SQLITE_OK is returned if everything goes according to plan. An
** SQLITE_IOERR_XXX error code is returned if a call to sqlite3OsOpen()
** fails.
*/
static int openSubJournal(Pager *pPager){
int rc = SQLITE_OK;
if( !isOpen(pPager->sjfd) ){
const int flags = SQLITE_OPEN_SUBJOURNAL | SQLITE_OPEN_READWRITE
| SQLITE_OPEN_CREATE | SQLITE_OPEN_EXCLUSIVE
| SQLITE_OPEN_DELETEONCLOSE;
int nStmtSpill = sqlite3Config.nStmtSpill;
if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY || pPager->subjInMemory ){
nStmtSpill = -1;
}
rc = sqlite3JournalOpen(pPager->pVfs, 0, pPager->sjfd, flags, nStmtSpill);
}
return rc;
}
/*
** Append a record of the current state of page pPg to the sub-journal.
**
** If successful, set the bit corresponding to pPg->pgno in the bitvecs
** for all open savepoints before returning.
**
** This function returns SQLITE_OK if everything is successful, an IO
** error code if the attempt to write to the sub-journal fails, or
** SQLITE_NOMEM if a malloc fails while setting a bit in a savepoint
** bitvec.
*/
static int subjournalPage(PgHdr *pPg){
int rc = SQLITE_OK;
Pager *pPager = pPg->pPager;
if( pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
/* Open the sub-journal, if it has not already been opened */
assert( pPager->useJournal );
assert( isOpen(pPager->jfd) || pagerUseWal(pPager) );
assert( isOpen(pPager->sjfd) || pPager->nSubRec==0 );
assert( pagerUseWal(pPager)
|| pageInJournal(pPager, pPg)
|| pPg->pgno>pPager->dbOrigSize
);
rc = openSubJournal(pPager);
/* If the sub-journal was opened successfully (or was already open),
** write the journal record into the file. */
if( rc==SQLITE_OK ){
void *pData = pPg->pData;
i64 offset = (i64)pPager->nSubRec*(4+pPager->pageSize);
char *pData2;
pData2 = pData;
PAGERTRACE(("STMT-JOURNAL %d page %d\n", PAGERID(pPager), pPg->pgno));
rc = write32bits(pPager->sjfd, offset, pPg->pgno);
if( rc==SQLITE_OK ){
rc = sqlite3OsWrite(pPager->sjfd, pData2, pPager->pageSize, offset+4);
}
}
}
if( rc==SQLITE_OK ){
pPager->nSubRec++;
assert( pPager->nSavepoint>0 );
rc = addToSavepointBitvecs(pPager, pPg->pgno);
}
return rc;
}
static int subjournalPageIfRequired(PgHdr *pPg){
if( subjRequiresPage(pPg) ){
return subjournalPage(pPg);
}else{
return SQLITE_OK;
}
}
/*
** This function is called by the pcache layer when it has reached some
** soft memory limit. The first argument is a pointer to a Pager object
** (cast as a void*). The pager is always 'purgeable' (not an in-memory
** database). The second argument is a reference to a page that is
** currently dirty but has no outstanding references. The page
** is always associated with the Pager object passed as the first
** argument.
**
** The job of this function is to make pPg clean by writing its contents
** out to the database file, if possible. This may involve syncing the
** journal file.
**
** If successful, sqlite3PcacheMakeClean() is called on the page and
** SQLITE_OK returned. If an IO error occurs while trying to make the
** page clean, the IO error code is returned. If the page cannot be
** made clean for some other reason, but no error occurs, then SQLITE_OK
** is returned by sqlite3PcacheMakeClean() is not called.
*/
static int pagerStress(void *p, PgHdr *pPg){
Pager *pPager = (Pager *)p;
int rc = SQLITE_OK;
assert( pPg->pPager==pPager );
assert( pPg->flags&PGHDR_DIRTY );
/* The doNotSpill NOSYNC bit is set during times when doing a sync of
** journal (and adding a new header) is not allowed. This occurs
** during calls to sqlite3PagerWrite() while trying to journal multiple
** pages belonging to the same sector.
**
** The doNotSpill ROLLBACK and OFF bits inhibits all cache spilling
** regardless of whether or not a sync is required. This is set during
** a rollback or by user request, respectively.
**
** Spilling is also prohibited when in an error state since that could
** lead to database corruption. In the current implementation it
** is impossible for sqlite3PcacheFetch() to be called with createFlag==3
** while in the error state, hence it is impossible for this routine to
** be called in the error state. Nevertheless, we include a NEVER()
** test for the error state as a safeguard against future changes.
*/
if( NEVER(pPager->errCode) ) return SQLITE_OK;
testcase( pPager->doNotSpill & SPILLFLAG_ROLLBACK );
testcase( pPager->doNotSpill & SPILLFLAG_OFF );
testcase( pPager->doNotSpill & SPILLFLAG_NOSYNC );
if( pPager->doNotSpill
&& ((pPager->doNotSpill & (SPILLFLAG_ROLLBACK|SPILLFLAG_OFF))!=0
|| (pPg->flags & PGHDR_NEED_SYNC)!=0)
){
return SQLITE_OK;
}
pPager->aStat[PAGER_STAT_SPILL]++;
pPg->pDirty = 0;
if( pagerUseWal(pPager) ){
/* Write a single frame for this page to the log. */
rc = subjournalPageIfRequired(pPg);
if( rc==SQLITE_OK ){
rc = pagerWalFrames(pPager, pPg, 0, 0);
}
}else{
#ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE
if( pPager->tempFile==0 ){
rc = sqlite3JournalCreate(pPager->jfd);
if( rc!=SQLITE_OK ) return pager_error(pPager, rc);
}
#endif
/* Sync the journal file if required. */
if( pPg->flags&PGHDR_NEED_SYNC
|| pPager->eState==PAGER_WRITER_CACHEMOD
){
rc = syncJournal(pPager, 1);
}
/* Write the contents of the page out to the database file. */
if( rc==SQLITE_OK ){
assert( (pPg->flags&PGHDR_NEED_SYNC)==0 );
rc = pager_write_pagelist(pPager, pPg);
}
}
/* Mark the page as clean. */
if( rc==SQLITE_OK ){
PAGERTRACE(("STRESS %d page %d\n", PAGERID(pPager), pPg->pgno));
sqlite3PcacheMakeClean(pPg);
}
return pager_error(pPager, rc);
}
/*
** Flush all unreferenced dirty pages to disk.
*/
int sqlite3PagerFlush(Pager *pPager){
int rc = pPager->errCode;
if( !MEMDB ){
PgHdr *pList = sqlite3PcacheDirtyList(pPager->pPCache);
assert( assert_pager_state(pPager) );
while( rc==SQLITE_OK && pList ){
PgHdr *pNext = pList->pDirty;
if( pList->nRef==0 ){
rc = pagerStress((void*)pPager, pList);
}
pList = pNext;
}
}
return rc;
}
/*
** Allocate and initialize a new Pager object and put a pointer to it
** in *ppPager. The pager should eventually be freed by passing it
** to sqlite3PagerClose().
**
** The zFilename argument is the path to the database file to open.
** If zFilename is NULL then a randomly-named temporary file is created
** and used as the file to be cached. Temporary files are be deleted
** automatically when they are closed. If zFilename is ":memory:" then
** all information is held in cache. It is never written to disk.
** This can be used to implement an in-memory database.
**
** The nExtra parameter specifies the number of bytes of space allocated
** along with each page reference. This space is available to the user
** via the sqlite3PagerGetExtra() API. When a new page is allocated, the
** first 8 bytes of this space are zeroed but the remainder is uninitialized.
** (The extra space is used by btree as the MemPage object.)
**
** The flags argument is used to specify properties that affect the
** operation of the pager. It should be passed some bitwise combination
** of the PAGER_* flags.
**
** The vfsFlags parameter is a bitmask to pass to the flags parameter
** of the xOpen() method of the supplied VFS when opening files.
**
** If the pager object is allocated and the specified file opened
** successfully, SQLITE_OK is returned and *ppPager set to point to
** the new pager object. If an error occurs, *ppPager is set to NULL
** and error code returned. This function may return SQLITE_NOMEM
** (sqlite3Malloc() is used to allocate memory), SQLITE_CANTOPEN or
** various SQLITE_IO_XXX errors.
*/
int sqlite3PagerOpen(
sqlite3_vfs *pVfs, /* The virtual file system to use */
Pager **ppPager, /* OUT: Return the Pager structure here */
const char *zFilename, /* Name of the database file to open */
int nExtra, /* Extra bytes append to each in-memory page */
int flags, /* flags controlling this file */
int vfsFlags, /* flags passed through to sqlite3_vfs.xOpen() */
void (*xReinit)(DbPage*) /* Function to reinitialize pages */
){
u8 *pPtr;
Pager *pPager = 0; /* Pager object to allocate and return */
int rc = SQLITE_OK; /* Return code */
int tempFile = 0; /* True for temp files (incl. in-memory files) */
int memDb = 0; /* True if this is an in-memory file */
int memJM = 0; /* Memory journal mode */
int readOnly = 0; /* True if this is a read-only file */
int journalFileSize; /* Bytes to allocate for each journal fd */
char *zPathname = 0; /* Full path to database file */
int nPathname = 0; /* Number of bytes in zPathname */
int useJournal = (flags & PAGER_OMIT_JOURNAL)==0; /* False to omit journal */
int pcacheSize = sqlite3PcacheSize(); /* Bytes to allocate for PCache */
u32 szPageDflt = SQLITE_DEFAULT_PAGE_SIZE; /* Default page size */
const char *zUri = 0; /* URI args to copy */
int nUriByte = 1; /* Number of bytes of URI args at *zUri */
/* Figure out how much space is required for each journal file-handle
** (there are two of them, the main journal and the sub-journal). */
journalFileSize = ROUND8(sqlite3JournalSize(pVfs));
/* Set the output variable to NULL in case an error occurs. */
*ppPager = 0;
#ifndef SQLITE_OMIT_MEMORYDB
if( flags & PAGER_MEMORY ){
memDb = 1;
if( zFilename && zFilename[0] ){
zPathname = sqlite3DbStrDup(0, zFilename);
if( zPathname==0 ) return SQLITE_NOMEM_BKPT;
nPathname = sqlite3Strlen30(zPathname);
zFilename = 0;
}
}
#endif
/* Compute and store the full pathname in an allocated buffer pointed
** to by zPathname, length nPathname. Or, if this is a temporary file,
** leave both nPathname and zPathname set to 0.
*/
if( zFilename && zFilename[0] ){
const char *z;
nPathname = pVfs->mxPathname+1;
zPathname = sqlite3DbMallocRaw(0, nPathname*2);
if( zPathname==0 ){
return SQLITE_NOMEM_BKPT;
}
zPathname[0] = 0; /* Make sure initialized even if FullPathname() fails */
rc = sqlite3OsFullPathname(pVfs, zFilename, nPathname, zPathname);
if( rc!=SQLITE_OK ){
if( rc==SQLITE_OK_SYMLINK ){
if( vfsFlags & SQLITE_OPEN_NOFOLLOW ){
rc = SQLITE_CANTOPEN_SYMLINK;
}else{
rc = SQLITE_OK;
}
}
}
nPathname = sqlite3Strlen30(zPathname);
z = zUri = &zFilename[sqlite3Strlen30(zFilename)+1];
while( *z ){
z += strlen(z)+1;
z += strlen(z)+1;
}
nUriByte = (int)(&z[1] - zUri);
assert( nUriByte>=1 );
if( rc==SQLITE_OK && nPathname+8>pVfs->mxPathname ){
/* This branch is taken when the journal path required by
** the database being opened will be more than pVfs->mxPathname
** bytes in length. This means the database cannot be opened,
** as it will not be possible to open the journal file or even
** check for a hot-journal before reading.
*/
rc = SQLITE_CANTOPEN_BKPT;
}
if( rc!=SQLITE_OK ){
sqlite3DbFree(0, zPathname);
return rc;
}
}
/* Allocate memory for the Pager structure, PCache object, the
** three file descriptors, the database file name and the journal
** file name. The layout in memory is as follows:
**
** Pager object (sizeof(Pager) bytes)
** PCache object (sqlite3PcacheSize() bytes)
** Database file handle (pVfs->szOsFile bytes)
** Sub-journal file handle (journalFileSize bytes)
** Main journal file handle (journalFileSize bytes)
** Ptr back to the Pager (sizeof(Pager*) bytes)
** \0\0\0\0 database prefix (4 bytes)
** Database file name (nPathname+1 bytes)
** URI query parameters (nUriByte bytes)
** Journal filename (nPathname+8+1 bytes)
** WAL filename (nPathname+4+1 bytes)
** \0\0\0 terminator (3 bytes)
**
** Some 3rd-party software, over which we have no control, depends on
** the specific order of the filenames and the \0 separators between them
** so that it can (for example) find the database filename given the WAL
** filename without using the sqlite3_filename_database() API. This is a
** misuse of SQLite and a bug in the 3rd-party software, but the 3rd-party
** software is in widespread use, so we try to avoid changing the filename
** order and formatting if possible. In particular, the details of the
** filename format expected by 3rd-party software should be as follows:
**
** - Main Database Path
** - \0
** - Multiple URI components consisting of:
** - Key
** - \0
** - Value
** - \0
** - \0
** - Journal Path
** - \0
** - WAL Path (zWALName)
** - \0
**
** The sqlite3_create_filename() interface and the databaseFilename() utility
** that is used by sqlite3_filename_database() and kin also depend on the
** specific formatting and order of the various filenames, so if the format
** changes here, be sure to change it there as well.
*/
assert( SQLITE_PTRSIZE==sizeof(Pager*) );
pPtr = (u8 *)sqlite3MallocZero(
ROUND8(sizeof(*pPager)) + /* Pager structure */
ROUND8(pcacheSize) + /* PCache object */
ROUND8(pVfs->szOsFile) + /* The main db file */
journalFileSize * 2 + /* The two journal files */
SQLITE_PTRSIZE + /* Space to hold a pointer */
4 + /* Database prefix */
nPathname + 1 + /* database filename */
nUriByte + /* query parameters */
nPathname + 8 + 1 + /* Journal filename */
#ifndef SQLITE_OMIT_WAL
nPathname + 4 + 1 + /* WAL filename */
#endif
3 /* Terminator */
);
assert( EIGHT_BYTE_ALIGNMENT(SQLITE_INT_TO_PTR(journalFileSize)) );
if( !pPtr ){
sqlite3DbFree(0, zPathname);
return SQLITE_NOMEM_BKPT;
}
pPager = (Pager*)pPtr; pPtr += ROUND8(sizeof(*pPager));
pPager->pPCache = (PCache*)pPtr; pPtr += ROUND8(pcacheSize);
pPager->fd = (sqlite3_file*)pPtr; pPtr += ROUND8(pVfs->szOsFile);
pPager->sjfd = (sqlite3_file*)pPtr; pPtr += journalFileSize;
pPager->jfd = (sqlite3_file*)pPtr; pPtr += journalFileSize;
assert( EIGHT_BYTE_ALIGNMENT(pPager->jfd) );
memcpy(pPtr, &pPager, SQLITE_PTRSIZE); pPtr += SQLITE_PTRSIZE;
/* Fill in the Pager.zFilename and pPager.zQueryParam fields */
pPtr += 4; /* Skip zero prefix */
pPager->zFilename = (char*)pPtr;
if( nPathname>0 ){
memcpy(pPtr, zPathname, nPathname); pPtr += nPathname + 1;
if( zUri ){
memcpy(pPtr, zUri, nUriByte); pPtr += nUriByte;
}else{
pPtr++;
}
}
/* Fill in Pager.zJournal */
if( nPathname>0 ){
pPager->zJournal = (char*)pPtr;
memcpy(pPtr, zPathname, nPathname); pPtr += nPathname;
memcpy(pPtr, "-journal",8); pPtr += 8 + 1;
#ifdef SQLITE_ENABLE_8_3_NAMES
sqlite3FileSuffix3(zFilename,pPager->zJournal);
pPtr = (u8*)(pPager->zJournal + sqlite3Strlen30(pPager->zJournal)+1);
#endif
}else{
pPager->zJournal = 0;
}
#ifndef SQLITE_OMIT_WAL
/* Fill in Pager.zWal */
if( nPathname>0 ){
pPager->zWal = (char*)pPtr;
memcpy(pPtr, zPathname, nPathname); pPtr += nPathname;
memcpy(pPtr, "-wal", 4); pPtr += 4 + 1;
#ifdef SQLITE_ENABLE_8_3_NAMES
sqlite3FileSuffix3(zFilename, pPager->zWal);
pPtr = (u8*)(pPager->zWal + sqlite3Strlen30(pPager->zWal)+1);
#endif
}else{
pPager->zWal = 0;
}
#endif
(void)pPtr; /* Suppress warning about unused pPtr value */
if( nPathname ) sqlite3DbFree(0, zPathname);
pPager->pVfs = pVfs;
pPager->vfsFlags = vfsFlags;
/* Open the pager file.
*/
if( zFilename && zFilename[0] ){
int fout = 0; /* VFS flags returned by xOpen() */
rc = sqlite3OsOpen(pVfs, pPager->zFilename, pPager->fd, vfsFlags, &fout);
assert( !memDb );
pPager->memVfs = memJM = (fout&SQLITE_OPEN_MEMORY)!=0;
readOnly = (fout&SQLITE_OPEN_READONLY)!=0;
/* If the file was successfully opened for read/write access,
** choose a default page size in case we have to create the
** database file. The default page size is the maximum of:
**
** + SQLITE_DEFAULT_PAGE_SIZE,
** + The value returned by sqlite3OsSectorSize()
** + The largest page size that can be written atomically.
*/
if( rc==SQLITE_OK ){
int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
if( !readOnly ){
setSectorSize(pPager);
assert(SQLITE_DEFAULT_PAGE_SIZE<=SQLITE_MAX_DEFAULT_PAGE_SIZE);
if( szPageDflt<pPager->sectorSize ){
if( pPager->sectorSize>SQLITE_MAX_DEFAULT_PAGE_SIZE ){
szPageDflt = SQLITE_MAX_DEFAULT_PAGE_SIZE;
}else{
szPageDflt = (u32)pPager->sectorSize;
}
}
#ifdef SQLITE_ENABLE_ATOMIC_WRITE
{
int ii;
assert(SQLITE_IOCAP_ATOMIC512==(512>>8));
assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8));
assert(SQLITE_MAX_DEFAULT_PAGE_SIZE<=65536);
for(ii=szPageDflt; ii<=SQLITE_MAX_DEFAULT_PAGE_SIZE; ii=ii*2){
if( iDc&(SQLITE_IOCAP_ATOMIC|(ii>>8)) ){
szPageDflt = ii;
}
}
}
#endif
}
pPager->noLock = sqlite3_uri_boolean(pPager->zFilename, "nolock", 0);
if( (iDc & SQLITE_IOCAP_IMMUTABLE)!=0
|| sqlite3_uri_boolean(pPager->zFilename, "immutable", 0) ){
vfsFlags |= SQLITE_OPEN_READONLY;
goto act_like_temp_file;
}
}
}else{
/* If a temporary file is requested, it is not opened immediately.
** In this case we accept the default page size and delay actually
** opening the file until the first call to OsWrite().
**
** This branch is also run for an in-memory database. An in-memory
** database is the same as a temp-file that is never written out to
** disk and uses an in-memory rollback journal.
**
** This branch also runs for files marked as immutable.
*/
act_like_temp_file:
tempFile = 1;
pPager->eState = PAGER_READER; /* Pretend we already have a lock */
pPager->eLock = EXCLUSIVE_LOCK; /* Pretend we are in EXCLUSIVE mode */
pPager->noLock = 1; /* Do no locking */
readOnly = (vfsFlags&SQLITE_OPEN_READONLY);
}
/* The following call to PagerSetPagesize() serves to set the value of
** Pager.pageSize and to allocate the Pager.pTmpSpace buffer.
*/
if( rc==SQLITE_OK ){
assert( pPager->memDb==0 );
rc = sqlite3PagerSetPagesize(pPager, &szPageDflt, -1);
testcase( rc!=SQLITE_OK );
}
/* Initialize the PCache object. */
if( rc==SQLITE_OK ){
nExtra = ROUND8(nExtra);
assert( nExtra>=8 && nExtra<1000 );
rc = sqlite3PcacheOpen(szPageDflt, nExtra, !memDb,
!memDb?pagerStress:0, (void *)pPager, pPager->pPCache);
}
/* If an error occurred above, free the Pager structure and close the file.
*/
if( rc!=SQLITE_OK ){
sqlite3OsClose(pPager->fd);
sqlite3PageFree(pPager->pTmpSpace);
sqlite3_free(pPager);
return rc;
}
PAGERTRACE(("OPEN %d %s\n", FILEHANDLEID(pPager->fd), pPager->zFilename));
IOTRACE(("OPEN %p %s\n", pPager, pPager->zFilename))
pPager->useJournal = (u8)useJournal;
/* pPager->stmtOpen = 0; */
/* pPager->stmtInUse = 0; */
/* pPager->nRef = 0; */
/* pPager->stmtSize = 0; */
/* pPager->stmtJSize = 0; */
/* pPager->nPage = 0; */
pPager->mxPgno = SQLITE_MAX_PAGE_COUNT;
/* pPager->state = PAGER_UNLOCK; */
/* pPager->errMask = 0; */
pPager->tempFile = (u8)tempFile;
assert( tempFile==PAGER_LOCKINGMODE_NORMAL
|| tempFile==PAGER_LOCKINGMODE_EXCLUSIVE );
assert( PAGER_LOCKINGMODE_EXCLUSIVE==1 );
pPager->exclusiveMode = (u8)tempFile;
pPager->changeCountDone = pPager->tempFile;
pPager->memDb = (u8)memDb;
pPager->readOnly = (u8)readOnly;
assert( useJournal || pPager->tempFile );
sqlite3PagerSetFlags(pPager, (SQLITE_DEFAULT_SYNCHRONOUS+1)|PAGER_CACHESPILL);
/* pPager->pFirst = 0; */
/* pPager->pFirstSynced = 0; */
/* pPager->pLast = 0; */
pPager->nExtra = (u16)nExtra;
pPager->journalSizeLimit = SQLITE_DEFAULT_JOURNAL_SIZE_LIMIT;
assert( isOpen(pPager->fd) || tempFile );
setSectorSize(pPager);
if( !useJournal ){
pPager->journalMode = PAGER_JOURNALMODE_OFF;
}else if( memDb || memJM ){
pPager->journalMode = PAGER_JOURNALMODE_MEMORY;
}
/* pPager->xBusyHandler = 0; */
/* pPager->pBusyHandlerArg = 0; */
pPager->xReiniter = xReinit;
setGetterMethod(pPager);
/* memset(pPager->aHash, 0, sizeof(pPager->aHash)); */
/* pPager->szMmap = SQLITE_DEFAULT_MMAP_SIZE // will be set by btree.c */
*ppPager = pPager;
return SQLITE_OK;
}
/*
** Return the sqlite3_file for the main database given the name
** of the corresponding WAL or Journal name as passed into
** xOpen.
*/
sqlite3_file *sqlite3_database_file_object(const char *zName){
Pager *pPager;
const char *p;
while( zName[-1]!=0 || zName[-2]!=0 || zName[-3]!=0 || zName[-4]!=0 ){
zName--;
}
p = zName - 4 - sizeof(Pager*);
assert( EIGHT_BYTE_ALIGNMENT(p) );
pPager = *(Pager**)p;
return pPager->fd;
}
/*
** This function is called after transitioning from PAGER_UNLOCK to
** PAGER_SHARED state. It tests if there is a hot journal present in
** the file-system for the given pager. A hot journal is one that
** needs to be played back. According to this function, a hot-journal
** file exists if the following criteria are met:
**
** * The journal file exists in the file system, and
** * No process holds a RESERVED or greater lock on the database file, and
** * The database file itself is greater than 0 bytes in size, and
** * The first byte of the journal file exists and is not 0x00.
**
** If the current size of the database file is 0 but a journal file
** exists, that is probably an old journal left over from a prior
** database with the same name. In this case the journal file is
** just deleted using OsDelete, *pExists is set to 0 and SQLITE_OK
** is returned.
**
** This routine does not check if there is a super-journal filename
** at the end of the file. If there is, and that super-journal file
** does not exist, then the journal file is not really hot. In this
** case this routine will return a false-positive. The pager_playback()
** routine will discover that the journal file is not really hot and
** will not roll it back.
**
** If a hot-journal file is found to exist, *pExists is set to 1 and
** SQLITE_OK returned. If no hot-journal file is present, *pExists is
** set to 0 and SQLITE_OK returned. If an IO error occurs while trying
** to determine whether or not a hot-journal file exists, the IO error
** code is returned and the value of *pExists is undefined.
*/
static int hasHotJournal(Pager *pPager, int *pExists){
sqlite3_vfs * const pVfs = pPager->pVfs;
int rc = SQLITE_OK; /* Return code */
int exists = 1; /* True if a journal file is present */
int jrnlOpen = !!isOpen(pPager->jfd);
assert( pPager->useJournal );
assert( isOpen(pPager->fd) );
assert( pPager->eState==PAGER_OPEN );
assert( jrnlOpen==0 || ( sqlite3OsDeviceCharacteristics(pPager->jfd) &
SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN
));
*pExists = 0;
if( !jrnlOpen ){
rc = sqlite3OsAccess(pVfs, pPager->zJournal, SQLITE_ACCESS_EXISTS, &exists);
}
if( rc==SQLITE_OK && exists ){
int locked = 0; /* True if some process holds a RESERVED lock */
/* Race condition here: Another process might have been holding the
** the RESERVED lock and have a journal open at the sqlite3OsAccess()
** call above, but then delete the journal and drop the lock before
** we get to the following sqlite3OsCheckReservedLock() call. If that
** is the case, this routine might think there is a hot journal when
** in fact there is none. This results in a false-positive which will
** be dealt with by the playback routine. Ticket #3883.
*/
rc = sqlite3OsCheckReservedLock(pPager->fd, &locked);
if( rc==SQLITE_OK && !locked ){
Pgno nPage; /* Number of pages in database file */
assert( pPager->tempFile==0 );
rc = pagerPagecount(pPager, &nPage);
if( rc==SQLITE_OK ){
/* If the database is zero pages in size, that means that either (1) the
** journal is a remnant from a prior database with the same name where
** the database file but not the journal was deleted, or (2) the initial
** transaction that populates a new database is being rolled back.
** In either case, the journal file can be deleted. However, take care
** not to delete the journal file if it is already open due to
** journal_mode=PERSIST.
*/
if( nPage==0 && !jrnlOpen ){
sqlite3BeginBenignMalloc();
if( pagerLockDb(pPager, RESERVED_LOCK)==SQLITE_OK ){
sqlite3OsDelete(pVfs, pPager->zJournal, 0);
if( !pPager->exclusiveMode ) pagerUnlockDb(pPager, SHARED_LOCK);
}
sqlite3EndBenignMalloc();
}else{
/* The journal file exists and no other connection has a reserved
** or greater lock on the database file. Now check that there is
** at least one non-zero bytes at the start of the journal file.
** If there is, then we consider this journal to be hot. If not,
** it can be ignored.
*/
if( !jrnlOpen ){
int f = SQLITE_OPEN_READONLY|SQLITE_OPEN_MAIN_JOURNAL;
rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &f);
}
if( rc==SQLITE_OK ){
u8 first = 0;
rc = sqlite3OsRead(pPager->jfd, (void *)&first, 1, 0);
if( rc==SQLITE_IOERR_SHORT_READ ){
rc = SQLITE_OK;
}
if( !jrnlOpen ){
sqlite3OsClose(pPager->jfd);
}
*pExists = (first!=0);
}else if( rc==SQLITE_CANTOPEN ){
/* If we cannot open the rollback journal file in order to see if
** it has a zero header, that might be due to an I/O error, or
** it might be due to the race condition described above and in
** ticket #3883. Either way, assume that the journal is hot.
** This might be a false positive. But if it is, then the
** automatic journal playback and recovery mechanism will deal
** with it under an EXCLUSIVE lock where we do not need to
** worry so much with race conditions.
*/
*pExists = 1;
rc = SQLITE_OK;
}
}
}
}
}
return rc;
}
/*
** This function is called to obtain a shared lock on the database file.
** It is illegal to call sqlite3PagerGet() until after this function
** has been successfully called. If a shared-lock is already held when
** this function is called, it is a no-op.
**
** The following operations are also performed by this function.
**
** 1) If the pager is currently in PAGER_OPEN state (no lock held
** on the database file), then an attempt is made to obtain a
** SHARED lock on the database file. Immediately after obtaining
** the SHARED lock, the file-system is checked for a hot-journal,
** which is played back if present. Following any hot-journal
** rollback, the contents of the cache are validated by checking
** the 'change-counter' field of the database file header and
** discarded if they are found to be invalid.
**
** 2) If the pager is running in exclusive-mode, and there are currently
** no outstanding references to any pages, and is in the error state,
** then an attempt is made to clear the error state by discarding
** the contents of the page cache and rolling back any open journal
** file.
**
** If everything is successful, SQLITE_OK is returned. If an IO error
** occurs while locking the database, checking for a hot-journal file or
** rolling back a journal file, the IO error code is returned.
*/
int sqlite3PagerSharedLock(Pager *pPager){
int rc = SQLITE_OK; /* Return code */
/* This routine is only called from b-tree and only when there are no
** outstanding pages. This implies that the pager state should either
** be OPEN or READER. READER is only possible if the pager is or was in
** exclusive access mode. */
assert( sqlite3PcacheRefCount(pPager->pPCache)==0 );
assert( assert_pager_state(pPager) );
assert( pPager->eState==PAGER_OPEN || pPager->eState==PAGER_READER );
assert( pPager->errCode==SQLITE_OK );
if( !pagerUseWal(pPager) && pPager->eState==PAGER_OPEN ){
int bHotJournal = 1; /* True if there exists a hot journal-file */
assert( !MEMDB );
assert( pPager->tempFile==0 || pPager->eLock==EXCLUSIVE_LOCK );
rc = pager_wait_on_lock(pPager, SHARED_LOCK);
if( rc!=SQLITE_OK ){
assert( pPager->eLock==NO_LOCK || pPager->eLock==UNKNOWN_LOCK );
goto failed;
}
/* If a journal file exists, and there is no RESERVED lock on the
** database file, then it either needs to be played back or deleted.
*/
if( pPager->eLock<=SHARED_LOCK ){
rc = hasHotJournal(pPager, &bHotJournal);
}
if( rc!=SQLITE_OK ){
goto failed;
}
if( bHotJournal ){
if( pPager->readOnly ){
rc = SQLITE_READONLY_ROLLBACK;
goto failed;
}
/* Get an EXCLUSIVE lock on the database file. At this point it is
** important that a RESERVED lock is not obtained on the way to the
** EXCLUSIVE lock. If it were, another process might open the
** database file, detect the RESERVED lock, and conclude that the
** database is safe to read while this process is still rolling the
** hot-journal back.
**
** Because the intermediate RESERVED lock is not requested, any
** other process attempting to access the database file will get to
** this point in the code and fail to obtain its own EXCLUSIVE lock
** on the database file.
**
** Unless the pager is in locking_mode=exclusive mode, the lock is
** downgraded to SHARED_LOCK before this function returns.
*/
rc = pagerLockDb(pPager, EXCLUSIVE_LOCK);
if( rc!=SQLITE_OK ){
goto failed;
}
/* If it is not already open and the file exists on disk, open the
** journal for read/write access. Write access is required because
** in exclusive-access mode the file descriptor will be kept open
** and possibly used for a transaction later on. Also, write-access
** is usually required to finalize the journal in journal_mode=persist
** mode (and also for journal_mode=truncate on some systems).
**
** If the journal does not exist, it usually means that some
** other connection managed to get in and roll it back before
** this connection obtained the exclusive lock above. Or, it
** may mean that the pager was in the error-state when this
** function was called and the journal file does not exist.
*/
if( !isOpen(pPager->jfd) && pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
sqlite3_vfs * const pVfs = pPager->pVfs;
int bExists; /* True if journal file exists */
rc = sqlite3OsAccess(
pVfs, pPager->zJournal, SQLITE_ACCESS_EXISTS, &bExists);
if( rc==SQLITE_OK && bExists ){
int fout = 0;
int f = SQLITE_OPEN_READWRITE|SQLITE_OPEN_MAIN_JOURNAL;
assert( !pPager->tempFile );
rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &fout);
assert( rc!=SQLITE_OK || isOpen(pPager->jfd) );
if( rc==SQLITE_OK && fout&SQLITE_OPEN_READONLY ){
rc = SQLITE_CANTOPEN_BKPT;
sqlite3OsClose(pPager->jfd);
}
}
}
/* Playback and delete the journal. Drop the database write
** lock and reacquire the read lock. Purge the cache before
** playing back the hot-journal so that we don't end up with
** an inconsistent cache. Sync the hot journal before playing
** it back since the process that crashed and left the hot journal
** probably did not sync it and we are required to always sync
** the journal before playing it back.
*/
if( isOpen(pPager->jfd) ){
assert( rc==SQLITE_OK );
rc = pagerSyncHotJournal(pPager);
if( rc==SQLITE_OK ){
rc = pager_playback(pPager, !pPager->tempFile);
pPager->eState = PAGER_OPEN;
}
}else if( !pPager->exclusiveMode ){
pagerUnlockDb(pPager, SHARED_LOCK);
}
if( rc!=SQLITE_OK ){
/* This branch is taken if an error occurs while trying to open
** or roll back a hot-journal while holding an EXCLUSIVE lock. The
** pager_unlock() routine will be called before returning to unlock
** the file. If the unlock attempt fails, then Pager.eLock must be
** set to UNKNOWN_LOCK (see the comment above the #define for
** UNKNOWN_LOCK above for an explanation).
**
** In order to get pager_unlock() to do this, set Pager.eState to
** PAGER_ERROR now. This is not actually counted as a transition
** to ERROR state in the state diagram at the top of this file,
** since we know that the same call to pager_unlock() will very
** shortly transition the pager object to the OPEN state. Calling
** assert_pager_state() would fail now, as it should not be possible
** to be in ERROR state when there are zero outstanding page
** references.
*/
pager_error(pPager, rc);
goto failed;
}
assert( pPager->eState==PAGER_OPEN );
assert( (pPager->eLock==SHARED_LOCK)
|| (pPager->exclusiveMode && pPager->eLock>SHARED_LOCK)
);
}
if( !pPager->tempFile && pPager->hasHeldSharedLock ){
/* The shared-lock has just been acquired then check to
** see if the database has been modified. If the database has changed,
** flush the cache. The hasHeldSharedLock flag prevents this from
** occurring on the very first access to a file, in order to save a
** single unnecessary sqlite3OsRead() call at the start-up.
**
** Database changes are detected by looking at 15 bytes beginning
** at offset 24 into the file. The first 4 of these 16 bytes are
** a 32-bit counter that is incremented with each change. The
** other bytes change randomly with each file change when
** a codec is in use.
**
** There is a vanishingly small chance that a change will not be
** detected. The chance of an undetected change is so small that
** it can be neglected.
*/
char dbFileVers[sizeof(pPager->dbFileVers)];
IOTRACE(("CKVERS %p %d\n", pPager, sizeof(dbFileVers)));
rc = sqlite3OsRead(pPager->fd, &dbFileVers, sizeof(dbFileVers), 24);
if( rc!=SQLITE_OK ){
if( rc!=SQLITE_IOERR_SHORT_READ ){
goto failed;
}
memset(dbFileVers, 0, sizeof(dbFileVers));
}
if( memcmp(pPager->dbFileVers, dbFileVers, sizeof(dbFileVers))!=0 ){
pager_reset(pPager);
/* Unmap the database file. It is possible that external processes
** may have truncated the database file and then extended it back
** to its original size while this process was not holding a lock.
** In this case there may exist a Pager.pMap mapping that appears
** to be the right size but is not actually valid. Avoid this
** possibility by unmapping the db here. */
if( USEFETCH(pPager) ){
sqlite3OsUnfetch(pPager->fd, 0, 0);
}
}
}
/* If there is a WAL file in the file-system, open this database in WAL
** mode. Otherwise, the following function call is a no-op.
*/
rc = pagerOpenWalIfPresent(pPager);
#ifndef SQLITE_OMIT_WAL
assert( pPager->pWal==0 || rc==SQLITE_OK );
#endif
}
if( pagerUseWal(pPager) ){
assert( rc==SQLITE_OK );
rc = pagerBeginReadTransaction(pPager);
}
if( pPager->tempFile==0 && pPager->eState==PAGER_OPEN && rc==SQLITE_OK ){
rc = pagerPagecount(pPager, &pPager->dbSize);
}
failed:
if( rc!=SQLITE_OK ){
assert( !MEMDB );
pager_unlock(pPager);
assert( pPager->eState==PAGER_OPEN );
}else{
pPager->eState = PAGER_READER;
pPager->hasHeldSharedLock = 1;
}
return rc;
}
/*
** If the reference count has reached zero, rollback any active
** transaction and unlock the pager.
**
** Except, in locking_mode=EXCLUSIVE when there is nothing to in
** the rollback journal, the unlock is not performed and there is
** nothing to rollback, so this routine is a no-op.
*/
static void pagerUnlockIfUnused(Pager *pPager){
if( sqlite3PcacheRefCount(pPager->pPCache)==0 ){
assert( pPager->nMmapOut==0 ); /* because page1 is never memory mapped */
pagerUnlockAndRollback(pPager);
}
}
/*
** The page getter methods each try to acquire a reference to a
** page with page number pgno. If the requested reference is
** successfully obtained, it is copied to *ppPage and SQLITE_OK returned.
**
** There are different implementations of the getter method depending
** on the current state of the pager.
**
** getPageNormal() -- The normal getter
** getPageError() -- Used if the pager is in an error state
** getPageMmap() -- Used if memory-mapped I/O is enabled
**
** If the requested page is already in the cache, it is returned.
** Otherwise, a new page object is allocated and populated with data
** read from the database file. In some cases, the pcache module may
** choose not to allocate a new page object and may reuse an existing
** object with no outstanding references.
**
** The extra data appended to a page is always initialized to zeros the
** first time a page is loaded into memory. If the page requested is
** already in the cache when this function is called, then the extra
** data is left as it was when the page object was last used.
**
** If the database image is smaller than the requested page or if
** the flags parameter contains the PAGER_GET_NOCONTENT bit and the
** requested page is not already stored in the cache, then no
** actual disk read occurs. In this case the memory image of the
** page is initialized to all zeros.
**
** If PAGER_GET_NOCONTENT is true, it means that we do not care about
** the contents of the page. This occurs in two scenarios:
**
** a) When reading a free-list leaf page from the database, and
**
** b) When a savepoint is being rolled back and we need to load
** a new page into the cache to be filled with the data read
** from the savepoint journal.
**
** If PAGER_GET_NOCONTENT is true, then the data returned is zeroed instead
** of being read from the database. Additionally, the bits corresponding
** to pgno in Pager.pInJournal (bitvec of pages already written to the
** journal file) and the PagerSavepoint.pInSavepoint bitvecs of any open
** savepoints are set. This means if the page is made writable at any
** point in the future, using a call to sqlite3PagerWrite(), its contents
** will not be journaled. This saves IO.
**
** The acquisition might fail for several reasons. In all cases,
** an appropriate error code is returned and *ppPage is set to NULL.
**
** See also sqlite3PagerLookup(). Both this routine and Lookup() attempt
** to find a page in the in-memory cache first. If the page is not already
** in memory, this routine goes to disk to read it in whereas Lookup()
** just returns 0. This routine acquires a read-lock the first time it
** has to go to disk, and could also playback an old journal if necessary.
** Since Lookup() never goes to disk, it never has to deal with locks
** or journal files.
*/
static int getPageNormal(
Pager *pPager, /* The pager open on the database file */
Pgno pgno, /* Page number to fetch */
DbPage **ppPage, /* Write a pointer to the page here */
int flags /* PAGER_GET_XXX flags */
){
int rc = SQLITE_OK;
PgHdr *pPg;
u8 noContent; /* True if PAGER_GET_NOCONTENT is set */
sqlite3_pcache_page *pBase;
assert( pPager->errCode==SQLITE_OK );
assert( pPager->eState>=PAGER_READER );
assert( assert_pager_state(pPager) );
assert( pPager->hasHeldSharedLock==1 );
if( pgno==0 ) return SQLITE_CORRUPT_BKPT;
pBase = sqlite3PcacheFetch(pPager->pPCache, pgno, 3);
if( pBase==0 ){
pPg = 0;
rc = sqlite3PcacheFetchStress(pPager->pPCache, pgno, &pBase);
if( rc!=SQLITE_OK ) goto pager_acquire_err;
if( pBase==0 ){
rc = SQLITE_NOMEM_BKPT;
goto pager_acquire_err;
}
}
pPg = *ppPage = sqlite3PcacheFetchFinish(pPager->pPCache, pgno, pBase);
assert( pPg==(*ppPage) );
assert( pPg->pgno==pgno );
assert( pPg->pPager==pPager || pPg->pPager==0 );
noContent = (flags & PAGER_GET_NOCONTENT)!=0;
if( pPg->pPager && !noContent ){
/* In this case the pcache already contains an initialized copy of
** the page. Return without further ado. */
assert( pgno!=PAGER_SJ_PGNO(pPager) );
pPager->aStat[PAGER_STAT_HIT]++;
return SQLITE_OK;
}else{
/* The pager cache has created a new page. Its content needs to
** be initialized. But first some error checks:
**
** (*) obsolete. Was: maximum page number is 2^31
** (2) Never try to fetch the locking page
*/
if( pgno==PAGER_SJ_PGNO(pPager) ){
rc = SQLITE_CORRUPT_BKPT;
goto pager_acquire_err;
}
pPg->pPager = pPager;
assert( !isOpen(pPager->fd) || !MEMDB );
if( !isOpen(pPager->fd) || pPager->dbSize<pgno || noContent ){
if( pgno>pPager->mxPgno ){
rc = SQLITE_FULL;
if( pgno<=pPager->dbSize ){
sqlite3PcacheRelease(pPg);
pPg = 0;
}
goto pager_acquire_err;
}
if( noContent ){
/* Failure to set the bits in the InJournal bit-vectors is benign.
** It merely means that we might do some extra work to journal a
** page that does not need to be journaled. Nevertheless, be sure
** to test the case where a malloc error occurs while trying to set
** a bit in a bit vector.
*/
sqlite3BeginBenignMalloc();
if( pgno<=pPager->dbOrigSize ){
TESTONLY( rc = ) sqlite3BitvecSet(pPager->pInJournal, pgno);
testcase( rc==SQLITE_NOMEM );
}
TESTONLY( rc = ) addToSavepointBitvecs(pPager, pgno);
testcase( rc==SQLITE_NOMEM );
sqlite3EndBenignMalloc();
}
memset(pPg->pData, 0, pPager->pageSize);
IOTRACE(("ZERO %p %d\n", pPager, pgno));
}else{
assert( pPg->pPager==pPager );
pPager->aStat[PAGER_STAT_MISS]++;
rc = readDbPage(pPg);
if( rc!=SQLITE_OK ){
goto pager_acquire_err;
}
}
pager_set_pagehash(pPg);
}
return SQLITE_OK;
pager_acquire_err:
assert( rc!=SQLITE_OK );
if( pPg ){
sqlite3PcacheDrop(pPg);
}
pagerUnlockIfUnused(pPager);
*ppPage = 0;
return rc;
}
#if SQLITE_MAX_MMAP_SIZE>0
/* The page getter for when memory-mapped I/O is enabled */
static int getPageMMap(
Pager *pPager, /* The pager open on the database file */
Pgno pgno, /* Page number to fetch */
DbPage **ppPage, /* Write a pointer to the page here */
int flags /* PAGER_GET_XXX flags */
){
int rc = SQLITE_OK;
PgHdr *pPg = 0;
u32 iFrame = 0; /* Frame to read from WAL file */
/* It is acceptable to use a read-only (mmap) page for any page except
** page 1 if there is no write-transaction open or the ACQUIRE_READONLY
** flag was specified by the caller. And so long as the db is not a
** temporary or in-memory database. */
const int bMmapOk = (pgno>1
&& (pPager->eState==PAGER_READER || (flags & PAGER_GET_READONLY))
);
assert( USEFETCH(pPager) );
/* Optimization note: Adding the "pgno<=1" term before "pgno==0" here
** allows the compiler optimizer to reuse the results of the "pgno>1"
** test in the previous statement, and avoid testing pgno==0 in the
** common case where pgno is large. */
if( pgno<=1 && pgno==0 ){
return SQLITE_CORRUPT_BKPT;
}
assert( pPager->eState>=PAGER_READER );
assert( assert_pager_state(pPager) );
assert( pPager->hasHeldSharedLock==1 );
assert( pPager->errCode==SQLITE_OK );
if( bMmapOk && pagerUseWal(pPager) ){
rc = sqlite3WalFindFrame(pPager->pWal, pgno, &iFrame);
if( rc!=SQLITE_OK ){
*ppPage = 0;
return rc;
}
}
if( bMmapOk && iFrame==0 ){
void *pData = 0;
rc = sqlite3OsFetch(pPager->fd,
(i64)(pgno-1) * pPager->pageSize, pPager->pageSize, &pData
);
if( rc==SQLITE_OK && pData ){
if( pPager->eState>PAGER_READER || pPager->tempFile ){
pPg = sqlite3PagerLookup(pPager, pgno);
}
if( pPg==0 ){
rc = pagerAcquireMapPage(pPager, pgno, pData, &pPg);
}else{
sqlite3OsUnfetch(pPager->fd, (i64)(pgno-1)*pPager->pageSize, pData);
}
if( pPg ){
assert( rc==SQLITE_OK );
*ppPage = pPg;
return SQLITE_OK;
}
}
if( rc!=SQLITE_OK ){
*ppPage = 0;
return rc;
}
}
return getPageNormal(pPager, pgno, ppPage, flags);
}
#endif /* SQLITE_MAX_MMAP_SIZE>0 */
/* The page getter method for when the pager is an error state */
static int getPageError(
Pager *pPager, /* The pager open on the database file */
Pgno pgno, /* Page number to fetch */
DbPage **ppPage, /* Write a pointer to the page here */
int flags /* PAGER_GET_XXX flags */
){
UNUSED_PARAMETER(pgno);
UNUSED_PARAMETER(flags);
assert( pPager->errCode!=SQLITE_OK );
*ppPage = 0;
return pPager->errCode;
}
/* Dispatch all page fetch requests to the appropriate getter method.
*/
int sqlite3PagerGet(
Pager *pPager, /* The pager open on the database file */
Pgno pgno, /* Page number to fetch */
DbPage **ppPage, /* Write a pointer to the page here */
int flags /* PAGER_GET_XXX flags */
){
#if 0 /* Trace page fetch by setting to 1 */
int rc;
printf("PAGE %u\n", pgno);
fflush(stdout);
rc = pPager->xGet(pPager, pgno, ppPage, flags);
if( rc ){
printf("PAGE %u failed with 0x%02x\n", pgno, rc);
fflush(stdout);
}
return rc;
#else
/* Normal, high-speed version of sqlite3PagerGet() */
return pPager->xGet(pPager, pgno, ppPage, flags);
#endif
}
/*
** Acquire a page if it is already in the in-memory cache. Do
** not read the page from disk. Return a pointer to the page,
** or 0 if the page is not in cache.
**
** See also sqlite3PagerGet(). The difference between this routine
** and sqlite3PagerGet() is that _get() will go to the disk and read
** in the page if the page is not already in cache. This routine
** returns NULL if the page is not in cache or if a disk I/O error
** has ever happened.
*/
DbPage *sqlite3PagerLookup(Pager *pPager, Pgno pgno){
sqlite3_pcache_page *pPage;
assert( pPager!=0 );
assert( pgno!=0 );
assert( pPager->pPCache!=0 );
pPage = sqlite3PcacheFetch(pPager->pPCache, pgno, 0);
assert( pPage==0 || pPager->hasHeldSharedLock );
if( pPage==0 ) return 0;
return sqlite3PcacheFetchFinish(pPager->pPCache, pgno, pPage);
}
/*
** Release a page reference.
**
** The sqlite3PagerUnref() and sqlite3PagerUnrefNotNull() may only be used
** if we know that the page being released is not the last reference to page1.
** The btree layer always holds page1 open until the end, so these first
** two routines can be used to release any page other than BtShared.pPage1.
** The assert() at tag-20230419-2 proves that this constraint is always
** honored.
**
** Use sqlite3PagerUnrefPageOne() to release page1. This latter routine
** checks the total number of outstanding pages and if the number of
** pages reaches zero it drops the database lock.
*/
void sqlite3PagerUnrefNotNull(DbPage *pPg){
TESTONLY( Pager *pPager = pPg->pPager; )
assert( pPg!=0 );
if( pPg->flags & PGHDR_MMAP ){
assert( pPg->pgno!=1 ); /* Page1 is never memory mapped */
pagerReleaseMapPage(pPg);
}else{
sqlite3PcacheRelease(pPg);
}
/* Do not use this routine to release the last reference to page1 */
assert( sqlite3PcacheRefCount(pPager->pPCache)>0 ); /* tag-20230419-2 */
}
void sqlite3PagerUnref(DbPage *pPg){
if( pPg ) sqlite3PagerUnrefNotNull(pPg);
}
void sqlite3PagerUnrefPageOne(DbPage *pPg){
Pager *pPager;
assert( pPg!=0 );
assert( pPg->pgno==1 );
assert( (pPg->flags & PGHDR_MMAP)==0 ); /* Page1 is never memory mapped */
pPager = pPg->pPager;
sqlite3PcacheRelease(pPg);
pagerUnlockIfUnused(pPager);
}
/*
** This function is called at the start of every write transaction.
** There must already be a RESERVED or EXCLUSIVE lock on the database
** file when this routine is called.
**
** Open the journal file for pager pPager and write a journal header
** to the start of it. If there are active savepoints, open the sub-journal
** as well. This function is only used when the journal file is being
** opened to write a rollback log for a transaction. It is not used
** when opening a hot journal file to roll it back.
**
** If the journal file is already open (as it may be in exclusive mode),
** then this function just writes a journal header to the start of the
** already open file.
**
** Whether or not the journal file is opened by this function, the
** Pager.pInJournal bitvec structure is allocated.
**
** Return SQLITE_OK if everything is successful. Otherwise, return
** SQLITE_NOMEM if the attempt to allocate Pager.pInJournal fails, or
** an IO error code if opening or writing the journal file fails.
*/
static int pager_open_journal(Pager *pPager){
int rc = SQLITE_OK; /* Return code */
sqlite3_vfs * const pVfs = pPager->pVfs; /* Local cache of vfs pointer */
assert( pPager->eState==PAGER_WRITER_LOCKED );
assert( assert_pager_state(pPager) );
assert( pPager->pInJournal==0 );
/* If already in the error state, this function is a no-op. But on
** the other hand, this routine is never called if we are already in
** an error state. */
if( NEVER(pPager->errCode) ) return pPager->errCode;
if( !pagerUseWal(pPager) && pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
pPager->pInJournal = sqlite3BitvecCreate(pPager->dbSize);
if( pPager->pInJournal==0 ){
return SQLITE_NOMEM_BKPT;
}
/* Open the journal file if it is not already open. */
if( !isOpen(pPager->jfd) ){
if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ){
sqlite3MemJournalOpen(pPager->jfd);
}else{
int flags = SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE;
int nSpill;
if( pPager->tempFile ){
flags |= (SQLITE_OPEN_DELETEONCLOSE|SQLITE_OPEN_TEMP_JOURNAL);
flags |= SQLITE_OPEN_EXCLUSIVE;
nSpill = sqlite3Config.nStmtSpill;
}else{
flags |= SQLITE_OPEN_MAIN_JOURNAL;
nSpill = jrnlBufferSize(pPager);
}
/* Verify that the database still has the same name as it did when
** it was originally opened. */
rc = databaseIsUnmoved(pPager);
if( rc==SQLITE_OK ){
rc = sqlite3JournalOpen (
pVfs, pPager->zJournal, pPager->jfd, flags, nSpill
);
}
}
assert( rc!=SQLITE_OK || isOpen(pPager->jfd) );
}
/* Write the first journal header to the journal file and open
** the sub-journal if necessary.
*/
if( rc==SQLITE_OK ){
/* TODO: Check if all of these are really required. */
pPager->nRec = 0;
pPager->journalOff = 0;
pPager->setSuper = 0;
pPager->journalHdr = 0;
rc = writeJournalHdr(pPager);
}
}
if( rc!=SQLITE_OK ){
sqlite3BitvecDestroy(pPager->pInJournal);
pPager->pInJournal = 0;
pPager->journalOff = 0;
}else{
assert( pPager->eState==PAGER_WRITER_LOCKED );
pPager->eState = PAGER_WRITER_CACHEMOD;
}
return rc;
}
/*
** Begin a write-transaction on the specified pager object. If a
** write-transaction has already been opened, this function is a no-op.
**
** If the exFlag argument is false, then acquire at least a RESERVED
** lock on the database file. If exFlag is true, then acquire at least
** an EXCLUSIVE lock. If such a lock is already held, no locking
** functions need be called.
**
** If the subjInMemory argument is non-zero, then any sub-journal opened
** within this transaction will be opened as an in-memory file. This
** has no effect if the sub-journal is already opened (as it may be when
** running in exclusive mode) or if the transaction does not require a
** sub-journal. If the subjInMemory argument is zero, then any required
** sub-journal is implemented in-memory if pPager is an in-memory database,
** or using a temporary file otherwise.
*/
int sqlite3PagerBegin(Pager *pPager, int exFlag, int subjInMemory){
int rc = SQLITE_OK;
if( pPager->errCode ) return pPager->errCode;
assert( pPager->eState>=PAGER_READER && pPager->eState<PAGER_ERROR );
pPager->subjInMemory = (u8)subjInMemory;
if( pPager->eState==PAGER_READER ){
assert( pPager->pInJournal==0 );
if( pagerUseWal(pPager) ){
/* If the pager is configured to use locking_mode=exclusive, and an
** exclusive lock on the database is not already held, obtain it now.
*/
if( pPager->exclusiveMode && sqlite3WalExclusiveMode(pPager->pWal, -1) ){
rc = pagerLockDb(pPager, EXCLUSIVE_LOCK);
if( rc!=SQLITE_OK ){
return rc;
}
(void)sqlite3WalExclusiveMode(pPager->pWal, 1);
}
/* Grab the write lock on the log file. If successful, upgrade to
** PAGER_RESERVED state. Otherwise, return an error code to the caller.
** The busy-handler is not invoked if another connection already
** holds the write-lock. If possible, the upper layer will call it.
*/
rc = sqlite3WalBeginWriteTransaction(pPager->pWal);
}else{
/* Obtain a RESERVED lock on the database file. If the exFlag parameter
** is true, then immediately upgrade this to an EXCLUSIVE lock. The
** busy-handler callback can be used when upgrading to the EXCLUSIVE
** lock, but not when obtaining the RESERVED lock.
*/
rc = pagerLockDb(pPager, RESERVED_LOCK);
if( rc==SQLITE_OK && exFlag ){
rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
}
}
if( rc==SQLITE_OK ){
/* Change to WRITER_LOCKED state.
**
** WAL mode sets Pager.eState to PAGER_WRITER_LOCKED or CACHEMOD
** when it has an open transaction, but never to DBMOD or FINISHED.
** This is because in those states the code to roll back savepoint
** transactions may copy data from the sub-journal into the database
** file as well as into the page cache. Which would be incorrect in
** WAL mode.
*/
pPager->eState = PAGER_WRITER_LOCKED;
pPager->dbHintSize = pPager->dbSize;
pPager->dbFileSize = pPager->dbSize;
pPager->dbOrigSize = pPager->dbSize;
pPager->journalOff = 0;
}
assert( rc==SQLITE_OK || pPager->eState==PAGER_READER );
assert( rc!=SQLITE_OK || pPager->eState==PAGER_WRITER_LOCKED );
assert( assert_pager_state(pPager) );
}
PAGERTRACE(("TRANSACTION %d\n", PAGERID(pPager)));
return rc;
}
/*
** Write page pPg onto the end of the rollback journal.
*/
static SQLITE_NOINLINE int pagerAddPageToRollbackJournal(PgHdr *pPg){
Pager *pPager = pPg->pPager;
int rc;
u32 cksum;
char *pData2;
i64 iOff = pPager->journalOff;
/* We should never write to the journal file the page that
** contains the database locks. The following assert verifies
** that we do not. */
assert( pPg->pgno!=PAGER_SJ_PGNO(pPager) );
assert( pPager->journalHdr<=pPager->journalOff );
pData2 = pPg->pData;
cksum = pager_cksum(pPager, (u8*)pData2);
/* Even if an IO or diskfull error occurs while journalling the
** page in the block above, set the need-sync flag for the page.
** Otherwise, when the transaction is rolled back, the logic in
** playback_one_page() will think that the page needs to be restored
** in the database file. And if an IO error occurs while doing so,
** then corruption may follow.
*/
pPg->flags |= PGHDR_NEED_SYNC;
rc = write32bits(pPager->jfd, iOff, pPg->pgno);
if( rc!=SQLITE_OK ) return rc;
rc = sqlite3OsWrite(pPager->jfd, pData2, pPager->pageSize, iOff+4);
if( rc!=SQLITE_OK ) return rc;
rc = write32bits(pPager->jfd, iOff+pPager->pageSize+4, cksum);
if( rc!=SQLITE_OK ) return rc;
IOTRACE(("JOUT %p %d %lld %d\n", pPager, pPg->pgno,
pPager->journalOff, pPager->pageSize));
PAGER_INCR(sqlite3_pager_writej_count);
PAGERTRACE(("JOURNAL %d page %d needSync=%d hash(%08x)\n",
PAGERID(pPager), pPg->pgno,
((pPg->flags&PGHDR_NEED_SYNC)?1:0), pager_pagehash(pPg)));
pPager->journalOff += 8 + pPager->pageSize;
pPager->nRec++;
assert( pPager->pInJournal!=0 );
rc = sqlite3BitvecSet(pPager->pInJournal, pPg->pgno);
testcase( rc==SQLITE_NOMEM );
assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
rc |= addToSavepointBitvecs(pPager, pPg->pgno);
assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
return rc;
}
/*
** Mark a single data page as writeable. The page is written into the
** main journal or sub-journal as required. If the page is written into
** one of the journals, the corresponding bit is set in the
** Pager.pInJournal bitvec and the PagerSavepoint.pInSavepoint bitvecs
** of any open savepoints as appropriate.
*/
static int pager_write(PgHdr *pPg){
Pager *pPager = pPg->pPager;
int rc = SQLITE_OK;
/* This routine is not called unless a write-transaction has already
** been started. The journal file may or may not be open at this point.
** It is never called in the ERROR state.
*/
assert( pPager->eState==PAGER_WRITER_LOCKED
|| pPager->eState==PAGER_WRITER_CACHEMOD
|| pPager->eState==PAGER_WRITER_DBMOD
);
assert( assert_pager_state(pPager) );
assert( pPager->errCode==0 );
assert( pPager->readOnly==0 );
CHECK_PAGE(pPg);
/* The journal file needs to be opened. Higher level routines have already
** obtained the necessary locks to begin the write-transaction, but the
** rollback journal might not yet be open. Open it now if this is the case.
**
** This is done before calling sqlite3PcacheMakeDirty() on the page.
** Otherwise, if it were done after calling sqlite3PcacheMakeDirty(), then
** an error might occur and the pager would end up in WRITER_LOCKED state
** with pages marked as dirty in the cache.
*/
if( pPager->eState==PAGER_WRITER_LOCKED ){
rc = pager_open_journal(pPager);
if( rc!=SQLITE_OK ) return rc;
}
assert( pPager->eState>=PAGER_WRITER_CACHEMOD );
assert( assert_pager_state(pPager) );
/* Mark the page that is about to be modified as dirty. */
sqlite3PcacheMakeDirty(pPg);
/* If a rollback journal is in use, them make sure the page that is about
** to change is in the rollback journal, or if the page is a new page off
** then end of the file, make sure it is marked as PGHDR_NEED_SYNC.
*/
assert( (pPager->pInJournal!=0) == isOpen(pPager->jfd) );
if( pPager->pInJournal!=0
&& sqlite3BitvecTestNotNull(pPager->pInJournal, pPg->pgno)==0
){
assert( pagerUseWal(pPager)==0 );
if( pPg->pgno<=pPager->dbOrigSize ){
rc = pagerAddPageToRollbackJournal(pPg);
if( rc!=SQLITE_OK ){
return rc;
}
}else{
if( pPager->eState!=PAGER_WRITER_DBMOD ){
pPg->flags |= PGHDR_NEED_SYNC;
}
PAGERTRACE(("APPEND %d page %d needSync=%d\n",
PAGERID(pPager), pPg->pgno,
((pPg->flags&PGHDR_NEED_SYNC)?1:0)));
}
}
/* The PGHDR_DIRTY bit is set above when the page was added to the dirty-list
** and before writing the page into the rollback journal. Wait until now,
** after the page has been successfully journalled, before setting the
** PGHDR_WRITEABLE bit that indicates that the page can be safely modified.
*/
pPg->flags |= PGHDR_WRITEABLE;
/* If the statement journal is open and the page is not in it,
** then write the page into the statement journal.
*/
if( pPager->nSavepoint>0 ){
rc = subjournalPageIfRequired(pPg);
}
/* Update the database size and return. */
if( pPager->dbSize<pPg->pgno ){
pPager->dbSize = pPg->pgno;
}
return rc;
}
/*
** This is a variant of sqlite3PagerWrite() that runs when the sector size
** is larger than the page size. SQLite makes the (reasonable) assumption that
** all bytes of a sector are written together by hardware. Hence, all bytes of
** a sector need to be journalled in case of a power loss in the middle of
** a write.
**
** Usually, the sector size is less than or equal to the page size, in which
** case pages can be individually written. This routine only runs in the
** exceptional case where the page size is smaller than the sector size.
*/
static SQLITE_NOINLINE int pagerWriteLargeSector(PgHdr *pPg){
int rc = SQLITE_OK; /* Return code */
Pgno nPageCount; /* Total number of pages in database file */
Pgno pg1; /* First page of the sector pPg is located on. */
int nPage = 0; /* Number of pages starting at pg1 to journal */
int ii; /* Loop counter */
int needSync = 0; /* True if any page has PGHDR_NEED_SYNC */
Pager *pPager = pPg->pPager; /* The pager that owns pPg */
Pgno nPagePerSector = (pPager->sectorSize/pPager->pageSize);
/* Set the doNotSpill NOSYNC bit to 1. This is because we cannot allow
** a journal header to be written between the pages journaled by
** this function.
*/
assert( !MEMDB );
assert( (pPager->doNotSpill & SPILLFLAG_NOSYNC)==0 );
pPager->doNotSpill |= SPILLFLAG_NOSYNC;
/* This trick assumes that both the page-size and sector-size are
** an integer power of 2. It sets variable pg1 to the identifier
** of the first page of the sector pPg is located on.
*/
pg1 = ((pPg->pgno-1) & ~(nPagePerSector-1)) + 1;
nPageCount = pPager->dbSize;
if( pPg->pgno>nPageCount ){
nPage = (pPg->pgno - pg1)+1;
}else if( (pg1+nPagePerSector-1)>nPageCount ){
nPage = nPageCount+1-pg1;
}else{
nPage = nPagePerSector;
}
assert(nPage>0);
assert(pg1<=pPg->pgno);
assert((pg1+nPage)>pPg->pgno);
for(ii=0; ii<nPage && rc==SQLITE_OK; ii++){
Pgno pg = pg1+ii;
PgHdr *pPage;
if( pg==pPg->pgno || !sqlite3BitvecTest(pPager->pInJournal, pg) ){
if( pg!=PAGER_SJ_PGNO(pPager) ){
rc = sqlite3PagerGet(pPager, pg, &pPage, 0);
if( rc==SQLITE_OK ){
rc = pager_write(pPage);
if( pPage->flags&PGHDR_NEED_SYNC ){
needSync = 1;
}
sqlite3PagerUnrefNotNull(pPage);
}
}
}else if( (pPage = sqlite3PagerLookup(pPager, pg))!=0 ){
if( pPage->flags&PGHDR_NEED_SYNC ){
needSync = 1;
}
sqlite3PagerUnrefNotNull(pPage);
}
}
/* If the PGHDR_NEED_SYNC flag is set for any of the nPage pages
** starting at pg1, then it needs to be set for all of them. Because
** writing to any of these nPage pages may damage the others, the
** journal file must contain sync()ed copies of all of them
** before any of them can be written out to the database file.
*/
if( rc==SQLITE_OK && needSync ){
assert( !MEMDB );
for(ii=0; ii<nPage; ii++){
PgHdr *pPage = sqlite3PagerLookup(pPager, pg1+ii);
if( pPage ){
pPage->flags |= PGHDR_NEED_SYNC;
sqlite3PagerUnrefNotNull(pPage);
}
}
}
assert( (pPager->doNotSpill & SPILLFLAG_NOSYNC)!=0 );
pPager->doNotSpill &= ~SPILLFLAG_NOSYNC;
return rc;
}
/*
** Mark a data page as writeable. This routine must be called before
** making changes to a page. The caller must check the return value
** of this function and be careful not to change any page data unless
** this routine returns SQLITE_OK.
**
** The difference between this function and pager_write() is that this
** function also deals with the special case where 2 or more pages
** fit on a single disk sector. In this case all co-resident pages
** must have been written to the journal file before returning.
**
** If an error occurs, SQLITE_NOMEM or an IO error code is returned
** as appropriate. Otherwise, SQLITE_OK.
*/
int sqlite3PagerWrite(PgHdr *pPg){
Pager *pPager = pPg->pPager;
assert( (pPg->flags & PGHDR_MMAP)==0 );
assert( pPager->eState>=PAGER_WRITER_LOCKED );
assert( assert_pager_state(pPager) );
if( (pPg->flags & PGHDR_WRITEABLE)!=0 && pPager->dbSize>=pPg->pgno ){
if( pPager->nSavepoint ) return subjournalPageIfRequired(pPg);
return SQLITE_OK;
}else if( pPager->errCode ){
return pPager->errCode;
}else if( pPager->sectorSize > (u32)pPager->pageSize ){
assert( pPager->tempFile==0 );
return pagerWriteLargeSector(pPg);
}else{
return pager_write(pPg);
}
}
/*
** Return TRUE if the page given in the argument was previously passed
** to sqlite3PagerWrite(). In other words, return TRUE if it is ok
** to change the content of the page.
*/
#ifndef NDEBUG
int sqlite3PagerIswriteable(DbPage *pPg){
return pPg->flags & PGHDR_WRITEABLE;
}
#endif
/*
** A call to this routine tells the pager that it is not necessary to
** write the information on page pPg back to the disk, even though
** that page might be marked as dirty. This happens, for example, when
** the page has been added as a leaf of the freelist and so its
** content no longer matters.
**
** The overlying software layer calls this routine when all of the data
** on the given page is unused. The pager marks the page as clean so
** that it does not get written to disk.
**
** Tests show that this optimization can quadruple the speed of large
** DELETE operations.
**
** This optimization cannot be used with a temp-file, as the page may
** have been dirty at the start of the transaction. In that case, if
** memory pressure forces page pPg out of the cache, the data does need
** to be written out to disk so that it may be read back in if the
** current transaction is rolled back.
*/
void sqlite3PagerDontWrite(PgHdr *pPg){
Pager *pPager = pPg->pPager;
if( !pPager->tempFile && (pPg->flags&PGHDR_DIRTY) && pPager->nSavepoint==0 ){
PAGERTRACE(("DONT_WRITE page %d of %d\n", pPg->pgno, PAGERID(pPager)));
IOTRACE(("CLEAN %p %d\n", pPager, pPg->pgno))
pPg->flags |= PGHDR_DONT_WRITE;
pPg->flags &= ~PGHDR_WRITEABLE;
testcase( pPg->flags & PGHDR_NEED_SYNC );
pager_set_pagehash(pPg);
}
}
/*
** This routine is called to increment the value of the database file
** change-counter, stored as a 4-byte big-endian integer starting at
** byte offset 24 of the pager file. The secondary change counter at
** 92 is also updated, as is the SQLite version number at offset 96.
**
** But this only happens if the pPager->changeCountDone flag is false.
** To avoid excess churning of page 1, the update only happens once.
** See also the pager_write_changecounter() routine that does an
** unconditional update of the change counters.
**
** If the isDirectMode flag is zero, then this is done by calling
** sqlite3PagerWrite() on page 1, then modifying the contents of the
** page data. In this case the file will be updated when the current
** transaction is committed.
**
** The isDirectMode flag may only be non-zero if the library was compiled
** with the SQLITE_ENABLE_ATOMIC_WRITE macro defined. In this case,
** if isDirect is non-zero, then the database file is updated directly
** by writing an updated version of page 1 using a call to the
** sqlite3OsWrite() function.
*/
static int pager_incr_changecounter(Pager *pPager, int isDirectMode){
int rc = SQLITE_OK;
assert( pPager->eState==PAGER_WRITER_CACHEMOD
|| pPager->eState==PAGER_WRITER_DBMOD
);
assert( assert_pager_state(pPager) );
/* Declare and initialize constant integer 'isDirect'. If the
** atomic-write optimization is enabled in this build, then isDirect
** is initialized to the value passed as the isDirectMode parameter
** to this function. Otherwise, it is always set to zero.
**
** The idea is that if the atomic-write optimization is not
** enabled at compile time, the compiler can omit the tests of
** 'isDirect' below, as well as the block enclosed in the
** "if( isDirect )" condition.
*/
#ifndef SQLITE_ENABLE_ATOMIC_WRITE
# define DIRECT_MODE 0
assert( isDirectMode==0 );
UNUSED_PARAMETER(isDirectMode);
#else
# define DIRECT_MODE isDirectMode
#endif
if( !pPager->changeCountDone && pPager->dbSize>0 ){
PgHdr *pPgHdr; /* Reference to page 1 */
assert( !pPager->tempFile && isOpen(pPager->fd) );
/* Open page 1 of the file for writing. */
rc = sqlite3PagerGet(pPager, 1, &pPgHdr, 0);
assert( pPgHdr==0 || rc==SQLITE_OK );
/* If page one was fetched successfully, and this function is not
** operating in direct-mode, make page 1 writable. When not in
** direct mode, page 1 is always held in cache and hence the PagerGet()
** above is always successful - hence the ALWAYS on rc==SQLITE_OK.
*/
if( !DIRECT_MODE && ALWAYS(rc==SQLITE_OK) ){
rc = sqlite3PagerWrite(pPgHdr);
}
if( rc==SQLITE_OK ){
/* Actually do the update of the change counter */
pager_write_changecounter(pPgHdr);
/* If running in direct mode, write the contents of page 1 to the file. */
if( DIRECT_MODE ){
const void *zBuf;
assert( pPager->dbFileSize>0 );
zBuf = pPgHdr->pData;
if( rc==SQLITE_OK ){
rc = sqlite3OsWrite(pPager->fd, zBuf, pPager->pageSize, 0);
pPager->aStat[PAGER_STAT_WRITE]++;
}
if( rc==SQLITE_OK ){
/* Update the pager's copy of the change-counter. Otherwise, the
** next time a read transaction is opened the cache will be
** flushed (as the change-counter values will not match). */
const void *pCopy = (const void *)&((const char *)zBuf)[24];
memcpy(&pPager->dbFileVers, pCopy, sizeof(pPager->dbFileVers));
pPager->changeCountDone = 1;
}
}else{
pPager->changeCountDone = 1;
}
}
/* Release the page reference. */
sqlite3PagerUnref(pPgHdr);
}
return rc;
}
/*
** Sync the database file to disk. This is a no-op for in-memory databases
** or pages with the Pager.noSync flag set.
**
** If successful, or if called on a pager for which it is a no-op, this
** function returns SQLITE_OK. Otherwise, an IO error code is returned.
*/
int sqlite3PagerSync(Pager *pPager, const char *zSuper){
int rc = SQLITE_OK;
void *pArg = (void*)zSuper;
rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_SYNC, pArg);
if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK;
if( rc==SQLITE_OK && !pPager->noSync ){
assert( !MEMDB );
rc = sqlite3OsSync(pPager->fd, pPager->syncFlags);
}
return rc;
}
/*
** This function may only be called while a write-transaction is active in
** rollback. If the connection is in WAL mode, this call is a no-op.
** Otherwise, if the connection does not already have an EXCLUSIVE lock on
** the database file, an attempt is made to obtain one.
**
** If the EXCLUSIVE lock is already held or the attempt to obtain it is
** successful, or the connection is in WAL mode, SQLITE_OK is returned.
** Otherwise, either SQLITE_BUSY or an SQLITE_IOERR_XXX error code is
** returned.
*/
int sqlite3PagerExclusiveLock(Pager *pPager){
int rc = pPager->errCode;
assert( assert_pager_state(pPager) );
if( rc==SQLITE_OK ){
assert( pPager->eState==PAGER_WRITER_CACHEMOD
|| pPager->eState==PAGER_WRITER_DBMOD
|| pPager->eState==PAGER_WRITER_LOCKED
);
assert( assert_pager_state(pPager) );
if( 0==pagerUseWal(pPager) ){
rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
}
}
return rc;
}
/*
** Sync the database file for the pager pPager. zSuper points to the name
** of a super-journal file that should be written into the individual
** journal file. zSuper may be NULL, which is interpreted as no
** super-journal (a single database transaction).
**
** This routine ensures that:
**
** * The database file change-counter is updated,
** * the journal is synced (unless the atomic-write optimization is used),
** * all dirty pages are written to the database file,
** * the database file is truncated (if required), and
** * the database file synced.
**
** The only thing that remains to commit the transaction is to finalize
** (delete, truncate or zero the first part of) the journal file (or
** delete the super-journal file if specified).
**
** Note that if zSuper==NULL, this does not overwrite a previous value
** passed to an sqlite3PagerCommitPhaseOne() call.
**
** If the final parameter - noSync - is true, then the database file itself
** is not synced. The caller must call sqlite3PagerSync() directly to
** sync the database file before calling CommitPhaseTwo() to delete the
** journal file in this case.
*/
int sqlite3PagerCommitPhaseOne(
Pager *pPager, /* Pager object */
const char *zSuper, /* If not NULL, the super-journal name */
int noSync /* True to omit the xSync on the db file */
){
int rc = SQLITE_OK; /* Return code */
assert( pPager->eState==PAGER_WRITER_LOCKED
|| pPager->eState==PAGER_WRITER_CACHEMOD
|| pPager->eState==PAGER_WRITER_DBMOD
|| pPager->eState==PAGER_ERROR
);
assert( assert_pager_state(pPager) );
/* If a prior error occurred, report that error again. */
if( NEVER(pPager->errCode) ) return pPager->errCode;
/* Provide the ability to easily simulate an I/O error during testing */
if( sqlite3FaultSim(400) ) return SQLITE_IOERR;
PAGERTRACE(("DATABASE SYNC: File=%s zSuper=%s nSize=%d\n",
pPager->zFilename, zSuper, pPager->dbSize));
/* If no database changes have been made, return early. */
if( pPager->eState<PAGER_WRITER_CACHEMOD ) return SQLITE_OK;
assert( MEMDB==0 || pPager->tempFile );
assert( isOpen(pPager->fd) || pPager->tempFile );
if( 0==pagerFlushOnCommit(pPager, 1) ){
/* If this is an in-memory db, or no pages have been written to, or this
** function has already been called, it is mostly a no-op. However, any
** backup in progress needs to be restarted. */
sqlite3BackupRestart(pPager->pBackup);
}else{
PgHdr *pList;
if( pagerUseWal(pPager) ){
PgHdr *pPageOne = 0;
pList = sqlite3PcacheDirtyList(pPager->pPCache);
if( pList==0 ){
/* Must have at least one page for the WAL commit flag.
** Ticket [2d1a5c67dfc2363e44f29d9bbd57f] 2011-05-18 */
rc = sqlite3PagerGet(pPager, 1, &pPageOne, 0);
pList = pPageOne;
pList->pDirty = 0;
}
assert( rc==SQLITE_OK );
if( ALWAYS(pList) ){
rc = pagerWalFrames(pPager, pList, pPager->dbSize, 1);
}
sqlite3PagerUnref(pPageOne);
if( rc==SQLITE_OK ){
sqlite3PcacheCleanAll(pPager->pPCache);
}
}else{
/* The bBatch boolean is true if the batch-atomic-write commit method
** should be used. No rollback journal is created if batch-atomic-write
** is enabled.
*/
#ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE
sqlite3_file *fd = pPager->fd;
int bBatch = zSuper==0 /* An SQLITE_IOCAP_BATCH_ATOMIC commit */
&& (sqlite3OsDeviceCharacteristics(fd) & SQLITE_IOCAP_BATCH_ATOMIC)
&& !pPager->noSync
&& sqlite3JournalIsInMemory(pPager->jfd);
#else
# define bBatch 0
#endif
#ifdef SQLITE_ENABLE_ATOMIC_WRITE
/* The following block updates the change-counter. Exactly how it
** does this depends on whether or not the atomic-update optimization
** was enabled at compile time, and if this transaction meets the
** runtime criteria to use the operation:
**
** * The file-system supports the atomic-write property for
** blocks of size page-size, and
** * This commit is not part of a multi-file transaction, and
** * Exactly one page has been modified and store in the journal file.
**
** If the optimization was not enabled at compile time, then the
** pager_incr_changecounter() function is called to update the change
** counter in 'indirect-mode'. If the optimization is compiled in but
** is not applicable to this transaction, call sqlite3JournalCreate()
** to make sure the journal file has actually been created, then call
** pager_incr_changecounter() to update the change-counter in indirect
** mode.
**
** Otherwise, if the optimization is both enabled and applicable,
** then call pager_incr_changecounter() to update the change-counter
** in 'direct' mode. In this case the journal file will never be
** created for this transaction.
*/
if( bBatch==0 ){
PgHdr *pPg;
assert( isOpen(pPager->jfd)
|| pPager->journalMode==PAGER_JOURNALMODE_OFF
|| pPager->journalMode==PAGER_JOURNALMODE_WAL
);
if( !zSuper && isOpen(pPager->jfd)
&& pPager->journalOff==jrnlBufferSize(pPager)
&& pPager->dbSize>=pPager->dbOrigSize
&& (!(pPg = sqlite3PcacheDirtyList(pPager->pPCache)) || 0==pPg->pDirty)
){
/* Update the db file change counter via the direct-write method. The
** following call will modify the in-memory representation of page 1
** to include the updated change counter and then write page 1
** directly to the database file. Because of the atomic-write
** property of the host file-system, this is safe.
*/
rc = pager_incr_changecounter(pPager, 1);
}else{
rc = sqlite3JournalCreate(pPager->jfd);
if( rc==SQLITE_OK ){
rc = pager_incr_changecounter(pPager, 0);
}
}
}
#else /* SQLITE_ENABLE_ATOMIC_WRITE */
#ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE
if( zSuper ){
rc = sqlite3JournalCreate(pPager->jfd);
if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
assert( bBatch==0 );
}
#endif
rc = pager_incr_changecounter(pPager, 0);
#endif /* !SQLITE_ENABLE_ATOMIC_WRITE */
if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
/* Write the super-journal name into the journal file. If a
** super-journal file name has already been written to the journal file,
** or if zSuper is NULL (no super-journal), then this call is a no-op.
*/
rc = writeSuperJournal(pPager, zSuper);
if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
/* Sync the journal file and write all dirty pages to the database.
** If the atomic-update optimization is being used, this sync will not
** create the journal file or perform any real IO.
**
** Because the change-counter page was just modified, unless the
** atomic-update optimization is used it is almost certain that the
** journal requires a sync here. However, in locking_mode=exclusive
** on a system under memory pressure it is just possible that this is
** not the case. In this case it is likely enough that the redundant
** xSync() call will be changed to a no-op by the OS anyhow.
*/
rc = syncJournal(pPager, 0);
if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
pList = sqlite3PcacheDirtyList(pPager->pPCache);
#ifdef SQLITE_ENABLE_BATCH_ATOMIC_WRITE
if( bBatch ){
rc = sqlite3OsFileControl(fd, SQLITE_FCNTL_BEGIN_ATOMIC_WRITE, 0);
if( rc==SQLITE_OK ){
rc = pager_write_pagelist(pPager, pList);
if( rc==SQLITE_OK && pPager->dbSize>pPager->dbFileSize ){
char *pTmp = pPager->pTmpSpace;
int szPage = (int)pPager->pageSize;
memset(pTmp, 0, szPage);
rc = sqlite3OsWrite(pPager->fd, pTmp, szPage,
((i64)pPager->dbSize*pPager->pageSize)-szPage);
}
if( rc==SQLITE_OK ){
rc = sqlite3OsFileControl(fd, SQLITE_FCNTL_COMMIT_ATOMIC_WRITE, 0);
}
if( rc!=SQLITE_OK ){
sqlite3OsFileControlHint(fd, SQLITE_FCNTL_ROLLBACK_ATOMIC_WRITE, 0);
}
}
if( (rc&0xFF)==SQLITE_IOERR && rc!=SQLITE_IOERR_NOMEM ){
rc = sqlite3JournalCreate(pPager->jfd);
if( rc!=SQLITE_OK ){
sqlite3OsClose(pPager->jfd);
goto commit_phase_one_exit;
}
bBatch = 0;
}else{
sqlite3OsClose(pPager->jfd);
}
}
#endif /* SQLITE_ENABLE_BATCH_ATOMIC_WRITE */
if( bBatch==0 ){
rc = pager_write_pagelist(pPager, pList);
}
if( rc!=SQLITE_OK ){
assert( rc!=SQLITE_IOERR_BLOCKED );
goto commit_phase_one_exit;
}
sqlite3PcacheCleanAll(pPager->pPCache);
/* If the file on disk is smaller than the database image, use
** pager_truncate to grow the file here. This can happen if the database
** image was extended as part of the current transaction and then the
** last page in the db image moved to the free-list. In this case the
** last page is never written out to disk, leaving the database file
** undersized. Fix this now if it is the case. */
if( pPager->dbSize>pPager->dbFileSize ){
Pgno nNew = pPager->dbSize - (pPager->dbSize==PAGER_SJ_PGNO(pPager));
assert( pPager->eState==PAGER_WRITER_DBMOD );
rc = pager_truncate(pPager, nNew);
if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
}
/* Finally, sync the database file. */
if( !noSync ){
rc = sqlite3PagerSync(pPager, zSuper);
}
IOTRACE(("DBSYNC %p\n", pPager))
}
}
commit_phase_one_exit:
if( rc==SQLITE_OK && !pagerUseWal(pPager) ){
pPager->eState = PAGER_WRITER_FINISHED;
}
return rc;
}
/*
** When this function is called, the database file has been completely
** updated to reflect the changes made by the current transaction and
** synced to disk. The journal file still exists in the file-system
** though, and if a failure occurs at this point it will eventually
** be used as a hot-journal and the current transaction rolled back.
**
** This function finalizes the journal file, either by deleting,
** truncating or partially zeroing it, so that it cannot be used
** for hot-journal rollback. Once this is done the transaction is
** irrevocably committed.
**
** If an error occurs, an IO error code is returned and the pager
** moves into the error state. Otherwise, SQLITE_OK is returned.
*/
int sqlite3PagerCommitPhaseTwo(Pager *pPager){
int rc = SQLITE_OK; /* Return code */
/* This routine should not be called if a prior error has occurred.
** But if (due to a coding error elsewhere in the system) it does get
** called, just return the same error code without doing anything. */
if( NEVER(pPager->errCode) ) return pPager->errCode;
pPager->iDataVersion++;
assert( pPager->eState==PAGER_WRITER_LOCKED
|| pPager->eState==PAGER_WRITER_FINISHED
|| (pagerUseWal(pPager) && pPager->eState==PAGER_WRITER_CACHEMOD)
);
assert( assert_pager_state(pPager) );
/* An optimization. If the database was not actually modified during
** this transaction, the pager is running in exclusive-mode and is
** using persistent journals, then this function is a no-op.
**
** The start of the journal file currently contains a single journal
** header with the nRec field set to 0. If such a journal is used as
** a hot-journal during hot-journal rollback, 0 changes will be made
** to the database file. So there is no need to zero the journal
** header. Since the pager is in exclusive mode, there is no need
** to drop any locks either.
*/
if( pPager->eState==PAGER_WRITER_LOCKED
&& pPager->exclusiveMode
&& pPager->journalMode==PAGER_JOURNALMODE_PERSIST
){
assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) || !pPager->journalOff );
pPager->eState = PAGER_READER;
return SQLITE_OK;
}
PAGERTRACE(("COMMIT %d\n", PAGERID(pPager)));
rc = pager_end_transaction(pPager, pPager->setSuper, 1);
return pager_error(pPager, rc);
}
/*
** If a write transaction is open, then all changes made within the
** transaction are reverted and the current write-transaction is closed.
** The pager falls back to PAGER_READER state if successful, or PAGER_ERROR
** state if an error occurs.
**
** If the pager is already in PAGER_ERROR state when this function is called,
** it returns Pager.errCode immediately. No work is performed in this case.
**
** Otherwise, in rollback mode, this function performs two functions:
**
** 1) It rolls back the journal file, restoring all database file and
** in-memory cache pages to the state they were in when the transaction
** was opened, and
**
** 2) It finalizes the journal file, so that it is not used for hot
** rollback at any point in the future.
**
** Finalization of the journal file (task 2) is only performed if the
** rollback is successful.
**
** In WAL mode, all cache-entries containing data modified within the
** current transaction are either expelled from the cache or reverted to
** their pre-transaction state by re-reading data from the database or
** WAL files. The WAL transaction is then closed.
*/
int sqlite3PagerRollback(Pager *pPager){
int rc = SQLITE_OK; /* Return code */
PAGERTRACE(("ROLLBACK %d\n", PAGERID(pPager)));
/* PagerRollback() is a no-op if called in READER or OPEN state. If
** the pager is already in the ERROR state, the rollback is not
** attempted here. Instead, the error code is returned to the caller.
*/
assert( assert_pager_state(pPager) );
if( pPager->eState==PAGER_ERROR ) return pPager->errCode;
if( pPager->eState<=PAGER_READER ) return SQLITE_OK;
if( pagerUseWal(pPager) ){
int rc2;
rc = sqlite3PagerSavepoint(pPager, SAVEPOINT_ROLLBACK, -1);
rc2 = pager_end_transaction(pPager, pPager->setSuper, 0);
if( rc==SQLITE_OK ) rc = rc2;
}else if( !isOpen(pPager->jfd) || pPager->eState==PAGER_WRITER_LOCKED ){
int eState = pPager->eState;
rc = pager_end_transaction(pPager, 0, 0);
if( !MEMDB && eState>PAGER_WRITER_LOCKED ){
/* This can happen using journal_mode=off. Move the pager to the error
** state to indicate that the contents of the cache may not be trusted.
** Any active readers will get SQLITE_ABORT.
*/
pPager->errCode = SQLITE_ABORT;
pPager->eState = PAGER_ERROR;
setGetterMethod(pPager);
return rc;
}
}else{
rc = pager_playback(pPager, 0);
}
assert( pPager->eState==PAGER_READER || rc!=SQLITE_OK );
assert( rc==SQLITE_OK || rc==SQLITE_FULL || rc==SQLITE_CORRUPT
|| rc==SQLITE_NOMEM || (rc&0xFF)==SQLITE_IOERR
|| rc==SQLITE_CANTOPEN
);
/* If an error occurs during a ROLLBACK, we can no longer trust the pager
** cache. So call pager_error() on the way out to make any error persistent.
*/
return pager_error(pPager, rc);
}
/*
** Return TRUE if the database file is opened read-only. Return FALSE
** if the database is (in theory) writable.
*/
u8 sqlite3PagerIsreadonly(Pager *pPager){
return pPager->readOnly;
}
#ifdef SQLITE_DEBUG
/*
** Return the sum of the reference counts for all pages held by pPager.
*/
int sqlite3PagerRefcount(Pager *pPager){
return sqlite3PcacheRefCount(pPager->pPCache);
}
#endif
/*
** Return the approximate number of bytes of memory currently
** used by the pager and its associated cache.
*/
int sqlite3PagerMemUsed(Pager *pPager){
int perPageSize = pPager->pageSize + pPager->nExtra
+ (int)(sizeof(PgHdr) + 5*sizeof(void*));
return perPageSize*sqlite3PcachePagecount(pPager->pPCache)
+ sqlite3MallocSize(pPager)
+ pPager->pageSize;
}
/*
** Return the number of references to the specified page.
*/
int sqlite3PagerPageRefcount(DbPage *pPage){
return sqlite3PcachePageRefcount(pPage);
}
#ifdef SQLITE_TEST
/*
** This routine is used for testing and analysis only.
*/
int *sqlite3PagerStats(Pager *pPager){
static int a[11];
a[0] = sqlite3PcacheRefCount(pPager->pPCache);
a[1] = sqlite3PcachePagecount(pPager->pPCache);
a[2] = sqlite3PcacheGetCachesize(pPager->pPCache);
a[3] = pPager->eState==PAGER_OPEN ? -1 : (int) pPager->dbSize;
a[4] = pPager->eState;
a[5] = pPager->errCode;
a[6] = (int)pPager->aStat[PAGER_STAT_HIT] & 0x7fffffff;
a[7] = (int)pPager->aStat[PAGER_STAT_MISS] & 0x7fffffff;
a[8] = 0; /* Used to be pPager->nOvfl */
a[9] = pPager->nRead;
a[10] = (int)pPager->aStat[PAGER_STAT_WRITE] & 0x7fffffff;
return a;
}
#endif
/*
** Parameter eStat must be one of SQLITE_DBSTATUS_CACHE_HIT, _MISS, _WRITE,
** or _WRITE+1. The SQLITE_DBSTATUS_CACHE_WRITE+1 case is a translation
** of SQLITE_DBSTATUS_CACHE_SPILL. The _SPILL case is not contiguous because
** it was added later.
**
** Before returning, *pnVal is incremented by the
** current cache hit or miss count, according to the value of eStat. If the
** reset parameter is non-zero, the cache hit or miss count is zeroed before
** returning.
*/
void sqlite3PagerCacheStat(Pager *pPager, int eStat, int reset, u64 *pnVal){
assert( eStat==SQLITE_DBSTATUS_CACHE_HIT
|| eStat==SQLITE_DBSTATUS_CACHE_MISS
|| eStat==SQLITE_DBSTATUS_CACHE_WRITE
|| eStat==SQLITE_DBSTATUS_CACHE_WRITE+1
);
assert( SQLITE_DBSTATUS_CACHE_HIT+1==SQLITE_DBSTATUS_CACHE_MISS );
assert( SQLITE_DBSTATUS_CACHE_HIT+2==SQLITE_DBSTATUS_CACHE_WRITE );
assert( PAGER_STAT_HIT==0 && PAGER_STAT_MISS==1
&& PAGER_STAT_WRITE==2 && PAGER_STAT_SPILL==3 );
eStat -= SQLITE_DBSTATUS_CACHE_HIT;
*pnVal += pPager->aStat[eStat];
if( reset ){
pPager->aStat[eStat] = 0;
}
}
/*
** Return true if this is an in-memory or temp-file backed pager.
*/
int sqlite3PagerIsMemdb(Pager *pPager){
return pPager->tempFile || pPager->memVfs;
}
/*
** Check that there are at least nSavepoint savepoints open. If there are
** currently less than nSavepoints open, then open one or more savepoints
** to make up the difference. If the number of savepoints is already
** equal to nSavepoint, then this function is a no-op.
**
** If a memory allocation fails, SQLITE_NOMEM is returned. If an error
** occurs while opening the sub-journal file, then an IO error code is
** returned. Otherwise, SQLITE_OK.
*/
static SQLITE_NOINLINE int pagerOpenSavepoint(Pager *pPager, int nSavepoint){
int rc = SQLITE_OK; /* Return code */
int nCurrent = pPager->nSavepoint; /* Current number of savepoints */
int ii; /* Iterator variable */
PagerSavepoint *aNew; /* New Pager.aSavepoint array */
assert( pPager->eState>=PAGER_WRITER_LOCKED );
assert( assert_pager_state(pPager) );
assert( nSavepoint>nCurrent && pPager->useJournal );
/* Grow the Pager.aSavepoint array using realloc(). Return SQLITE_NOMEM
** if the allocation fails. Otherwise, zero the new portion in case a
** malloc failure occurs while populating it in the for(...) loop below.
*/
aNew = (PagerSavepoint *)sqlite3Realloc(
pPager->aSavepoint, sizeof(PagerSavepoint)*nSavepoint
);
if( !aNew ){
return SQLITE_NOMEM_BKPT;
}
memset(&aNew[nCurrent], 0, (nSavepoint-nCurrent) * sizeof(PagerSavepoint));
pPager->aSavepoint = aNew;
/* Populate the PagerSavepoint structures just allocated. */
for(ii=nCurrent; ii<nSavepoint; ii++){
aNew[ii].nOrig = pPager->dbSize;
if( isOpen(pPager->jfd) && pPager->journalOff>0 ){
aNew[ii].iOffset = pPager->journalOff;
}else{
aNew[ii].iOffset = JOURNAL_HDR_SZ(pPager);
}
aNew[ii].iSubRec = pPager->nSubRec;
aNew[ii].pInSavepoint = sqlite3BitvecCreate(pPager->dbSize);
aNew[ii].bTruncateOnRelease = 1;
if( !aNew[ii].pInSavepoint ){
return SQLITE_NOMEM_BKPT;
}
if( pagerUseWal(pPager) ){
sqlite3WalSavepoint(pPager->pWal, aNew[ii].aWalData);
}
pPager->nSavepoint = ii+1;
}
assert( pPager->nSavepoint==nSavepoint );
assertTruncateConstraint(pPager);
return rc;
}
int sqlite3PagerOpenSavepoint(Pager *pPager, int nSavepoint){
assert( pPager->eState>=PAGER_WRITER_LOCKED );
assert( assert_pager_state(pPager) );
if( nSavepoint>pPager->nSavepoint && pPager->useJournal ){
return pagerOpenSavepoint(pPager, nSavepoint);
}else{
return SQLITE_OK;
}
}
/*
** This function is called to rollback or release (commit) a savepoint.
** The savepoint to release or rollback need not be the most recently
** created savepoint.
**
** Parameter op is always either SAVEPOINT_ROLLBACK or SAVEPOINT_RELEASE.
** If it is SAVEPOINT_RELEASE, then release and destroy the savepoint with
** index iSavepoint. If it is SAVEPOINT_ROLLBACK, then rollback all changes
** that have occurred since the specified savepoint was created.
**
** The savepoint to rollback or release is identified by parameter
** iSavepoint. A value of 0 means to operate on the outermost savepoint
** (the first created). A value of (Pager.nSavepoint-1) means operate
** on the most recently created savepoint. If iSavepoint is greater than
** (Pager.nSavepoint-1), then this function is a no-op.
**
** If a negative value is passed to this function, then the current
** transaction is rolled back. This is different to calling
** sqlite3PagerRollback() because this function does not terminate
** the transaction or unlock the database, it just restores the
** contents of the database to its original state.
**
** In any case, all savepoints with an index greater than iSavepoint
** are destroyed. If this is a release operation (op==SAVEPOINT_RELEASE),
** then savepoint iSavepoint is also destroyed.
**
** This function may return SQLITE_NOMEM if a memory allocation fails,
** or an IO error code if an IO error occurs while rolling back a
** savepoint. If no errors occur, SQLITE_OK is returned.
*/
int sqlite3PagerSavepoint(Pager *pPager, int op, int iSavepoint){
int rc = pPager->errCode;
#ifdef SQLITE_ENABLE_ZIPVFS
if( op==SAVEPOINT_RELEASE ) rc = SQLITE_OK;
#endif
assert( op==SAVEPOINT_RELEASE || op==SAVEPOINT_ROLLBACK );
assert( iSavepoint>=0 || op==SAVEPOINT_ROLLBACK );
if( rc==SQLITE_OK && iSavepoint<pPager->nSavepoint ){
int ii; /* Iterator variable */
int nNew; /* Number of remaining savepoints after this op. */
/* Figure out how many savepoints will still be active after this
** operation. Store this value in nNew. Then free resources associated
** with any savepoints that are destroyed by this operation.
*/
nNew = iSavepoint + (( op==SAVEPOINT_RELEASE ) ? 0 : 1);
for(ii=nNew; ii<pPager->nSavepoint; ii++){
sqlite3BitvecDestroy(pPager->aSavepoint[ii].pInSavepoint);
}
pPager->nSavepoint = nNew;
/* Truncate the sub-journal so that it only includes the parts
** that are still in use. */
if( op==SAVEPOINT_RELEASE ){
PagerSavepoint *pRel = &pPager->aSavepoint[nNew];
if( pRel->bTruncateOnRelease && isOpen(pPager->sjfd) ){
/* Only truncate if it is an in-memory sub-journal. */
if( sqlite3JournalIsInMemory(pPager->sjfd) ){
i64 sz = (pPager->pageSize+4)*(i64)pRel->iSubRec;
rc = sqlite3OsTruncate(pPager->sjfd, sz);
assert( rc==SQLITE_OK );
}
pPager->nSubRec = pRel->iSubRec;
}
}
/* Else this is a rollback operation, playback the specified savepoint.
** If this is a temp-file, it is possible that the journal file has
** not yet been opened. In this case there have been no changes to
** the database file, so the playback operation can be skipped.
*/
else if( pagerUseWal(pPager) || isOpen(pPager->jfd) ){
PagerSavepoint *pSavepoint = (nNew==0)?0:&pPager->aSavepoint[nNew-1];
rc = pagerPlaybackSavepoint(pPager, pSavepoint);
assert(rc!=SQLITE_DONE);
}
#ifdef SQLITE_ENABLE_ZIPVFS
/* If the cache has been modified but the savepoint cannot be rolled
** back journal_mode=off, put the pager in the error state. This way,
** if the VFS used by this pager includes ZipVFS, the entire transaction
** can be rolled back at the ZipVFS level. */
else if(
pPager->journalMode==PAGER_JOURNALMODE_OFF
&& pPager->eState>=PAGER_WRITER_CACHEMOD
){
pPager->errCode = SQLITE_ABORT;
pPager->eState = PAGER_ERROR;
setGetterMethod(pPager);
}
#endif
}
return rc;
}
/*
** Return the full pathname of the database file.
**
** Except, if the pager is in-memory only, then return an empty string if
** nullIfMemDb is true. This routine is called with nullIfMemDb==1 when
** used to report the filename to the user, for compatibility with legacy
** behavior. But when the Btree needs to know the filename for matching to
** shared cache, it uses nullIfMemDb==0 so that in-memory databases can
** participate in shared-cache.
**
** The return value to this routine is always safe to use with
** sqlite3_uri_parameter() and sqlite3_filename_database() and friends.
*/
const char *sqlite3PagerFilename(const Pager *pPager, int nullIfMemDb){
static const char zFake[8] = { 0, 0, 0, 0, 0, 0, 0, 0 };
if( nullIfMemDb && (pPager->memDb || sqlite3IsMemdb(pPager->pVfs)) ){
return &zFake[4];
}else{
return pPager->zFilename;
}
}
/*
** Return the VFS structure for the pager.
*/
sqlite3_vfs *sqlite3PagerVfs(Pager *pPager){
return pPager->pVfs;
}
/*
** Return the file handle for the database file associated
** with the pager. This might return NULL if the file has
** not yet been opened.
*/
sqlite3_file *sqlite3PagerFile(Pager *pPager){
return pPager->fd;
}
/*
** Return the file handle for the journal file (if it exists).
** This will be either the rollback journal or the WAL file.
*/
sqlite3_file *sqlite3PagerJrnlFile(Pager *pPager){
#ifdef SQLITE_OMIT_WAL
return pPager->jfd;
#else
return pPager->pWal ? sqlite3WalFile(pPager->pWal) : pPager->jfd;
#endif
}
/*
** Return the full pathname of the journal file.
*/
const char *sqlite3PagerJournalname(Pager *pPager){
return pPager->zJournal;
}
#ifndef SQLITE_OMIT_AUTOVACUUM
/*
** Move the page pPg to location pgno in the file.
**
** There must be no references to the page previously located at
** pgno (which we call pPgOld) though that page is allowed to be
** in cache. If the page previously located at pgno is not already
** in the rollback journal, it is not put there by by this routine.
**
** References to the page pPg remain valid. Updating any
** meta-data associated with pPg (i.e. data stored in the nExtra bytes
** allocated along with the page) is the responsibility of the caller.
**
** A transaction must be active when this routine is called. It used to be
** required that a statement transaction was not active, but this restriction
** has been removed (CREATE INDEX needs to move a page when a statement
** transaction is active).
**
** If the fourth argument, isCommit, is non-zero, then this page is being
** moved as part of a database reorganization just before the transaction
** is being committed. In this case, it is guaranteed that the database page
** pPg refers to will not be written to again within this transaction.
**
** This function may return SQLITE_NOMEM or an IO error code if an error
** occurs. Otherwise, it returns SQLITE_OK.
*/
int sqlite3PagerMovepage(Pager *pPager, DbPage *pPg, Pgno pgno, int isCommit){
PgHdr *pPgOld; /* The page being overwritten. */
Pgno needSyncPgno = 0; /* Old value of pPg->pgno, if sync is required */
int rc; /* Return code */
Pgno origPgno; /* The original page number */
assert( pPg->nRef>0 );
assert( pPager->eState==PAGER_WRITER_CACHEMOD
|| pPager->eState==PAGER_WRITER_DBMOD
);
assert( assert_pager_state(pPager) );
/* In order to be able to rollback, an in-memory database must journal
** the page we are moving from.
*/
assert( pPager->tempFile || !MEMDB );
if( pPager->tempFile ){
rc = sqlite3PagerWrite(pPg);
if( rc ) return rc;
}
/* If the page being moved is dirty and has not been saved by the latest
** savepoint, then save the current contents of the page into the
** sub-journal now. This is required to handle the following scenario:
**
** BEGIN;
** <journal page X, then modify it in memory>
** SAVEPOINT one;
** <Move page X to location Y>
** ROLLBACK TO one;
**
** If page X were not written to the sub-journal here, it would not
** be possible to restore its contents when the "ROLLBACK TO one"
** statement were is processed.
**
** subjournalPage() may need to allocate space to store pPg->pgno into
** one or more savepoint bitvecs. This is the reason this function
** may return SQLITE_NOMEM.
*/
if( (pPg->flags & PGHDR_DIRTY)!=0
&& SQLITE_OK!=(rc = subjournalPageIfRequired(pPg))
){
return rc;
}
PAGERTRACE(("MOVE %d page %d (needSync=%d) moves to %d\n",
PAGERID(pPager), pPg->pgno, (pPg->flags&PGHDR_NEED_SYNC)?1:0, pgno));
IOTRACE(("MOVE %p %d %d\n", pPager, pPg->pgno, pgno))
/* If the journal needs to be sync()ed before page pPg->pgno can
** be written to, store pPg->pgno in local variable needSyncPgno.
**
** If the isCommit flag is set, there is no need to remember that
** the journal needs to be sync()ed before database page pPg->pgno
** can be written to. The caller has already promised not to write to it.
*/
if( (pPg->flags&PGHDR_NEED_SYNC) && !isCommit ){
needSyncPgno = pPg->pgno;
assert( pPager->journalMode==PAGER_JOURNALMODE_OFF ||
pageInJournal(pPager, pPg) || pPg->pgno>pPager->dbOrigSize );
assert( pPg->flags&PGHDR_DIRTY );
}
/* If the cache contains a page with page-number pgno, remove it
** from its hash chain. Also, if the PGHDR_NEED_SYNC flag was set for
** page pgno before the 'move' operation, it needs to be retained
** for the page moved there.
*/
pPg->flags &= ~PGHDR_NEED_SYNC;
pPgOld = sqlite3PagerLookup(pPager, pgno);
assert( !pPgOld || pPgOld->nRef==1 || CORRUPT_DB );
if( pPgOld ){
if( NEVER(pPgOld->nRef>1) ){
sqlite3PagerUnrefNotNull(pPgOld);
return SQLITE_CORRUPT_BKPT;
}
pPg->flags |= (pPgOld->flags&PGHDR_NEED_SYNC);
if( pPager->tempFile ){
/* Do not discard pages from an in-memory database since we might
** need to rollback later. Just move the page out of the way. */
sqlite3PcacheMove(pPgOld, pPager->dbSize+1);
}else{
sqlite3PcacheDrop(pPgOld);
}
}
origPgno = pPg->pgno;
sqlite3PcacheMove(pPg, pgno);
sqlite3PcacheMakeDirty(pPg);
/* For an in-memory database, make sure the original page continues
** to exist, in case the transaction needs to roll back. Use pPgOld
** as the original page since it has already been allocated.
*/
if( pPager->tempFile && pPgOld ){
sqlite3PcacheMove(pPgOld, origPgno);
sqlite3PagerUnrefNotNull(pPgOld);
}
if( needSyncPgno ){
/* If needSyncPgno is non-zero, then the journal file needs to be
** sync()ed before any data is written to database file page needSyncPgno.
** Currently, no such page exists in the page-cache and the
** "is journaled" bitvec flag has been set. This needs to be remedied by
** loading the page into the pager-cache and setting the PGHDR_NEED_SYNC
** flag.
**
** If the attempt to load the page into the page-cache fails, (due
** to a malloc() or IO failure), clear the bit in the pInJournal[]
** array. Otherwise, if the page is loaded and written again in
** this transaction, it may be written to the database file before
** it is synced into the journal file. This way, it may end up in
** the journal file twice, but that is not a problem.
*/
PgHdr *pPgHdr;
rc = sqlite3PagerGet(pPager, needSyncPgno, &pPgHdr, 0);
if( rc!=SQLITE_OK ){
if( needSyncPgno<=pPager->dbOrigSize ){
assert( pPager->pTmpSpace!=0 );
sqlite3BitvecClear(pPager->pInJournal, needSyncPgno, pPager->pTmpSpace);
}
return rc;
}
pPgHdr->flags |= PGHDR_NEED_SYNC;
sqlite3PcacheMakeDirty(pPgHdr);
sqlite3PagerUnrefNotNull(pPgHdr);
}
return SQLITE_OK;
}
#endif
/*
** The page handle passed as the first argument refers to a dirty page
** with a page number other than iNew. This function changes the page's
** page number to iNew and sets the value of the PgHdr.flags field to
** the value passed as the third parameter.
*/
void sqlite3PagerRekey(DbPage *pPg, Pgno iNew, u16 flags){
assert( pPg->pgno!=iNew );
pPg->flags = flags;
sqlite3PcacheMove(pPg, iNew);
}
/*
** Return a pointer to the data for the specified page.
*/
void *sqlite3PagerGetData(DbPage *pPg){
assert( pPg->nRef>0 || pPg->pPager->memDb );
return pPg->pData;
}
/*
** Return a pointer to the Pager.nExtra bytes of "extra" space
** allocated along with the specified page.
*/
void *sqlite3PagerGetExtra(DbPage *pPg){
return pPg->pExtra;
}
/*
** Get/set the locking-mode for this pager. Parameter eMode must be one
** of PAGER_LOCKINGMODE_QUERY, PAGER_LOCKINGMODE_NORMAL or
** PAGER_LOCKINGMODE_EXCLUSIVE. If the parameter is not _QUERY, then
** the locking-mode is set to the value specified.
**
** The returned value is either PAGER_LOCKINGMODE_NORMAL or
** PAGER_LOCKINGMODE_EXCLUSIVE, indicating the current (possibly updated)
** locking-mode.
*/
int sqlite3PagerLockingMode(Pager *pPager, int eMode){
assert( eMode==PAGER_LOCKINGMODE_QUERY
|| eMode==PAGER_LOCKINGMODE_NORMAL
|| eMode==PAGER_LOCKINGMODE_EXCLUSIVE );
assert( PAGER_LOCKINGMODE_QUERY<0 );
assert( PAGER_LOCKINGMODE_NORMAL>=0 && PAGER_LOCKINGMODE_EXCLUSIVE>=0 );
assert( pPager->exclusiveMode || 0==sqlite3WalHeapMemory(pPager->pWal) );
if( eMode>=0 && !pPager->tempFile && !sqlite3WalHeapMemory(pPager->pWal) ){
pPager->exclusiveMode = (u8)eMode;
}
return (int)pPager->exclusiveMode;
}
/*
** Set the journal-mode for this pager. Parameter eMode must be one of:
**
** PAGER_JOURNALMODE_DELETE
** PAGER_JOURNALMODE_TRUNCATE
** PAGER_JOURNALMODE_PERSIST
** PAGER_JOURNALMODE_OFF
** PAGER_JOURNALMODE_MEMORY
** PAGER_JOURNALMODE_WAL
**
** The journalmode is set to the value specified if the change is allowed.
** The change may be disallowed for the following reasons:
**
** * An in-memory database can only have its journal_mode set to _OFF
** or _MEMORY.
**
** * Temporary databases cannot have _WAL journalmode.
**
** The returned indicate the current (possibly updated) journal-mode.
*/
int sqlite3PagerSetJournalMode(Pager *pPager, int eMode){
u8 eOld = pPager->journalMode; /* Prior journalmode */
/* The eMode parameter is always valid */
assert( eMode==PAGER_JOURNALMODE_DELETE /* 0 */
|| eMode==PAGER_JOURNALMODE_PERSIST /* 1 */
|| eMode==PAGER_JOURNALMODE_OFF /* 2 */
|| eMode==PAGER_JOURNALMODE_TRUNCATE /* 3 */
|| eMode==PAGER_JOURNALMODE_MEMORY /* 4 */
|| eMode==PAGER_JOURNALMODE_WAL /* 5 */ );
/* This routine is only called from the OP_JournalMode opcode, and
** the logic there will never allow a temporary file to be changed
** to WAL mode.
*/
assert( pPager->tempFile==0 || eMode!=PAGER_JOURNALMODE_WAL );
/* Do allow the journalmode of an in-memory database to be set to
** anything other than MEMORY or OFF
*/
if( MEMDB ){
assert( eOld==PAGER_JOURNALMODE_MEMORY || eOld==PAGER_JOURNALMODE_OFF );
if( eMode!=PAGER_JOURNALMODE_MEMORY && eMode!=PAGER_JOURNALMODE_OFF ){
eMode = eOld;
}
}
if( eMode!=eOld ){
/* Change the journal mode. */
assert( pPager->eState!=PAGER_ERROR );
pPager->journalMode = (u8)eMode;
/* When transitioning from TRUNCATE or PERSIST to any other journal
** mode except WAL, unless the pager is in locking_mode=exclusive mode,
** delete the journal file.
*/
assert( (PAGER_JOURNALMODE_TRUNCATE & 5)==1 );
assert( (PAGER_JOURNALMODE_PERSIST & 5)==1 );
assert( (PAGER_JOURNALMODE_DELETE & 5)==0 );
assert( (PAGER_JOURNALMODE_MEMORY & 5)==4 );
assert( (PAGER_JOURNALMODE_OFF & 5)==0 );
assert( (PAGER_JOURNALMODE_WAL & 5)==5 );
assert( isOpen(pPager->fd) || pPager->exclusiveMode );
if( !pPager->exclusiveMode && (eOld & 5)==1 && (eMode & 1)==0 ){
/* In this case we would like to delete the journal file. If it is
** not possible, then that is not a problem. Deleting the journal file
** here is an optimization only.
**
** Before deleting the journal file, obtain a RESERVED lock on the
** database file. This ensures that the journal file is not deleted
** while it is in use by some other client.
*/
sqlite3OsClose(pPager->jfd);
if( pPager->eLock>=RESERVED_LOCK ){
sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
}else{
int rc = SQLITE_OK;
int state = pPager->eState;
assert( state==PAGER_OPEN || state==PAGER_READER );
if( state==PAGER_OPEN ){
rc = sqlite3PagerSharedLock(pPager);
}
if( pPager->eState==PAGER_READER ){
assert( rc==SQLITE_OK );
rc = pagerLockDb(pPager, RESERVED_LOCK);
}
if( rc==SQLITE_OK ){
sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
}
if( rc==SQLITE_OK && state==PAGER_READER ){
pagerUnlockDb(pPager, SHARED_LOCK);
}else if( state==PAGER_OPEN ){
pager_unlock(pPager);
}
assert( state==pPager->eState );
}
}else if( eMode==PAGER_JOURNALMODE_OFF || eMode==PAGER_JOURNALMODE_MEMORY ){
sqlite3OsClose(pPager->jfd);
}
}
/* Return the new journal mode */
return (int)pPager->journalMode;
}
/*
** Return the current journal mode.
*/
int sqlite3PagerGetJournalMode(Pager *pPager){
return (int)pPager->journalMode;
}
/*
** Return TRUE if the pager is in a state where it is OK to change the
** journalmode. Journalmode changes can only happen when the database
** is unmodified.
*/
int sqlite3PagerOkToChangeJournalMode(Pager *pPager){
assert( assert_pager_state(pPager) );
if( pPager->eState>=PAGER_WRITER_CACHEMOD ) return 0;
if( NEVER(isOpen(pPager->jfd) && pPager->journalOff>0) ) return 0;
return 1;
}
/*
** Get/set the size-limit used for persistent journal files.
**
** Setting the size limit to -1 means no limit is enforced.
** An attempt to set a limit smaller than -1 is a no-op.
*/
i64 sqlite3PagerJournalSizeLimit(Pager *pPager, i64 iLimit){
if( iLimit>=-1 ){
pPager->journalSizeLimit = iLimit;
sqlite3WalLimit(pPager->pWal, iLimit);
}
return pPager->journalSizeLimit;
}
/*
** Return a pointer to the pPager->pBackup variable. The backup module
** in backup.c maintains the content of this variable. This module
** uses it opaquely as an argument to sqlite3BackupRestart() and
** sqlite3BackupUpdate() only.
*/
sqlite3_backup **sqlite3PagerBackupPtr(Pager *pPager){
return &pPager->pBackup;
}
#ifndef SQLITE_OMIT_VACUUM
/*
** Unless this is an in-memory or temporary database, clear the pager cache.
*/
void sqlite3PagerClearCache(Pager *pPager){
assert( MEMDB==0 || pPager->tempFile );
if( pPager->tempFile==0 ) pager_reset(pPager);
}
#endif
#ifndef SQLITE_OMIT_WAL
/*
** This function is called when the user invokes "PRAGMA wal_checkpoint",
** "PRAGMA wal_blocking_checkpoint" or calls the sqlite3_wal_checkpoint()
** or wal_blocking_checkpoint() API functions.
**
** Parameter eMode is one of SQLITE_CHECKPOINT_PASSIVE, FULL or RESTART.
*/
int sqlite3PagerCheckpoint(
Pager *pPager, /* Checkpoint on this pager */
sqlite3 *db, /* Db handle used to check for interrupts */
int eMode, /* Type of checkpoint */
int *pnLog, /* OUT: Final number of frames in log */
int *pnCkpt /* OUT: Final number of checkpointed frames */
){
int rc = SQLITE_OK;
if( pPager->pWal==0 && pPager->journalMode==PAGER_JOURNALMODE_WAL ){
/* This only happens when a database file is zero bytes in size opened and
** then "PRAGMA journal_mode=WAL" is run and then sqlite3_wal_checkpoint()
** is invoked without any intervening transactions. We need to start
** a transaction to initialize pWal. The PRAGMA table_list statement is
** used for this since it starts transactions on every database file,
** including all ATTACHed databases. This seems expensive for a single
** sqlite3_wal_checkpoint() call, but it happens very rarely.
** https://sqlite.org/forum/forumpost/fd0f19d229156939
*/
sqlite3_exec(db, "PRAGMA table_list",0,0,0);
}
if( pPager->pWal ){
rc = sqlite3WalCheckpoint(pPager->pWal, db, eMode,
(eMode==SQLITE_CHECKPOINT_PASSIVE ? 0 : pPager->xBusyHandler),
pPager->pBusyHandlerArg,
pPager->walSyncFlags, pPager->pageSize, (u8 *)pPager->pTmpSpace,
pnLog, pnCkpt
);
}
return rc;
}
int sqlite3PagerWalCallback(Pager *pPager){
return sqlite3WalCallback(pPager->pWal);
}
/*
** Return true if the underlying VFS for the given pager supports the
** primitives necessary for write-ahead logging.
*/
int sqlite3PagerWalSupported(Pager *pPager){
const sqlite3_io_methods *pMethods = pPager->fd->pMethods;
if( pPager->noLock ) return 0;
return pPager->exclusiveMode || (pMethods->iVersion>=2 && pMethods->xShmMap);
}
/*
** Attempt to take an exclusive lock on the database file. If a PENDING lock
** is obtained instead, immediately release it.
*/
static int pagerExclusiveLock(Pager *pPager){
int rc; /* Return code */
u8 eOrigLock; /* Original lock */
assert( pPager->eLock>=SHARED_LOCK );
eOrigLock = pPager->eLock;
rc = pagerLockDb(pPager, EXCLUSIVE_LOCK);
if( rc!=SQLITE_OK ){
/* If the attempt to grab the exclusive lock failed, release the
** pending lock that may have been obtained instead. */
pagerUnlockDb(pPager, eOrigLock);
}
return rc;
}
/*
** Call sqlite3WalOpen() to open the WAL handle. If the pager is in
** exclusive-locking mode when this function is called, take an EXCLUSIVE
** lock on the database file and use heap-memory to store the wal-index
** in. Otherwise, use the normal shared-memory.
*/
static int pagerOpenWal(Pager *pPager){
int rc = SQLITE_OK;
assert( pPager->pWal==0 && pPager->tempFile==0 );
assert( pPager->eLock==SHARED_LOCK || pPager->eLock==EXCLUSIVE_LOCK );
/* If the pager is already in exclusive-mode, the WAL module will use
** heap-memory for the wal-index instead of the VFS shared-memory
** implementation. Take the exclusive lock now, before opening the WAL
** file, to make sure this is safe.
*/
if( pPager->exclusiveMode ){
rc = pagerExclusiveLock(pPager);
}
/* Open the connection to the log file. If this operation fails,
** (e.g. due to malloc() failure), return an error code.
*/
if( rc==SQLITE_OK ){
rc = sqlite3WalOpen(pPager->pVfs,
pPager->fd, pPager->zWal, pPager->exclusiveMode,
pPager->journalSizeLimit, &pPager->pWal
);
}
pagerFixMaplimit(pPager);
return rc;
}
/*
** The caller must be holding a SHARED lock on the database file to call
** this function.
**
** If the pager passed as the first argument is open on a real database
** file (not a temp file or an in-memory database), and the WAL file
** is not already open, make an attempt to open it now. If successful,
** return SQLITE_OK. If an error occurs or the VFS used by the pager does
** not support the xShmXXX() methods, return an error code. *pbOpen is
** not modified in either case.
**
** If the pager is open on a temp-file (or in-memory database), or if
** the WAL file is already open, set *pbOpen to 1 and return SQLITE_OK
** without doing anything.
*/
int sqlite3PagerOpenWal(
Pager *pPager, /* Pager object */
int *pbOpen /* OUT: Set to true if call is a no-op */
){
int rc = SQLITE_OK; /* Return code */
assert( assert_pager_state(pPager) );
assert( pPager->eState==PAGER_OPEN || pbOpen );
assert( pPager->eState==PAGER_READER || !pbOpen );
assert( pbOpen==0 || *pbOpen==0 );
assert( pbOpen!=0 || (!pPager->tempFile && !pPager->pWal) );
if( !pPager->tempFile && !pPager->pWal ){
if( !sqlite3PagerWalSupported(pPager) ) return SQLITE_CANTOPEN;
/* Close any rollback journal previously open */
sqlite3OsClose(pPager->jfd);
rc = pagerOpenWal(pPager);
if( rc==SQLITE_OK ){
pPager->journalMode = PAGER_JOURNALMODE_WAL;
pPager->eState = PAGER_OPEN;
}
}else{
*pbOpen = 1;
}
return rc;
}
/*
** This function is called to close the connection to the log file prior
** to switching from WAL to rollback mode.
**
** Before closing the log file, this function attempts to take an
** EXCLUSIVE lock on the database file. If this cannot be obtained, an
** error (SQLITE_BUSY) is returned and the log connection is not closed.
** If successful, the EXCLUSIVE lock is not released before returning.
*/
int sqlite3PagerCloseWal(Pager *pPager, sqlite3 *db){
int rc = SQLITE_OK;
assert( pPager->journalMode==PAGER_JOURNALMODE_WAL );
/* If the log file is not already open, but does exist in the file-system,
** it may need to be checkpointed before the connection can switch to
** rollback mode. Open it now so this can happen.
*/
if( !pPager->pWal ){
int logexists = 0;
rc = pagerLockDb(pPager, SHARED_LOCK);
if( rc==SQLITE_OK ){
rc = sqlite3OsAccess(
pPager->pVfs, pPager->zWal, SQLITE_ACCESS_EXISTS, &logexists
);
}
if( rc==SQLITE_OK && logexists ){
rc = pagerOpenWal(pPager);
}
}
/* Checkpoint and close the log. Because an EXCLUSIVE lock is held on
** the database file, the log and log-summary files will be deleted.
*/
if( rc==SQLITE_OK && pPager->pWal ){
rc = pagerExclusiveLock(pPager);
if( rc==SQLITE_OK ){
rc = sqlite3WalClose(pPager->pWal, db, pPager->walSyncFlags,
pPager->pageSize, (u8*)pPager->pTmpSpace);
pPager->pWal = 0;
pagerFixMaplimit(pPager);
if( rc && !pPager->exclusiveMode ) pagerUnlockDb(pPager, SHARED_LOCK);
}
}
return rc;
}
#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
/*
** If pager pPager is a wal-mode database not in exclusive locking mode,
** invoke the sqlite3WalWriteLock() function on the associated Wal object
** with the same db and bLock parameters as were passed to this function.
** Return an SQLite error code if an error occurs, or SQLITE_OK otherwise.
*/
int sqlite3PagerWalWriteLock(Pager *pPager, int bLock){
int rc = SQLITE_OK;
if( pagerUseWal(pPager) && pPager->exclusiveMode==0 ){
rc = sqlite3WalWriteLock(pPager->pWal, bLock);
}
return rc;
}
/*
** Set the database handle used by the wal layer to determine if
** blocking locks are required.
*/
void sqlite3PagerWalDb(Pager *pPager, sqlite3 *db){
if( pagerUseWal(pPager) ){
sqlite3WalDb(pPager->pWal, db);
}
}
#endif
#ifdef SQLITE_ENABLE_SNAPSHOT
/*
** If this is a WAL database, obtain a snapshot handle for the snapshot
** currently open. Otherwise, return an error.
*/
int sqlite3PagerSnapshotGet(Pager *pPager, sqlite3_snapshot **ppSnapshot){
int rc = SQLITE_ERROR;
if( pPager->pWal ){
rc = sqlite3WalSnapshotGet(pPager->pWal, ppSnapshot);
}
return rc;
}
/*
** If this is a WAL database, store a pointer to pSnapshot. Next time a
** read transaction is opened, attempt to read from the snapshot it
** identifies. If this is not a WAL database, return an error.
*/
int sqlite3PagerSnapshotOpen(
Pager *pPager,
sqlite3_snapshot *pSnapshot
){
int rc = SQLITE_OK;
if( pPager->pWal ){
sqlite3WalSnapshotOpen(pPager->pWal, pSnapshot);
}else{
rc = SQLITE_ERROR;
}
return rc;
}
/*
** If this is a WAL database, call sqlite3WalSnapshotRecover(). If this
** is not a WAL database, return an error.
*/
int sqlite3PagerSnapshotRecover(Pager *pPager){
int rc;
if( pPager->pWal ){
rc = sqlite3WalSnapshotRecover(pPager->pWal);
}else{
rc = SQLITE_ERROR;
}
return rc;
}
/*
** The caller currently has a read transaction open on the database.
** If this is not a WAL database, SQLITE_ERROR is returned. Otherwise,
** this function takes a SHARED lock on the CHECKPOINTER slot and then
** checks if the snapshot passed as the second argument is still
** available. If so, SQLITE_OK is returned.
**
** If the snapshot is not available, SQLITE_ERROR is returned. Or, if
** the CHECKPOINTER lock cannot be obtained, SQLITE_BUSY. If any error
** occurs (any value other than SQLITE_OK is returned), the CHECKPOINTER
** lock is released before returning.
*/
int sqlite3PagerSnapshotCheck(Pager *pPager, sqlite3_snapshot *pSnapshot){
int rc;
if( pPager->pWal ){
rc = sqlite3WalSnapshotCheck(pPager->pWal, pSnapshot);
}else{
rc = SQLITE_ERROR;
}
return rc;
}
/*
** Release a lock obtained by an earlier successful call to
** sqlite3PagerSnapshotCheck().
*/
void sqlite3PagerSnapshotUnlock(Pager *pPager){
assert( pPager->pWal );
sqlite3WalSnapshotUnlock(pPager->pWal);
}
#endif /* SQLITE_ENABLE_SNAPSHOT */
#endif /* !SQLITE_OMIT_WAL */
#ifdef SQLITE_ENABLE_ZIPVFS
/*
** A read-lock must be held on the pager when this function is called. If
** the pager is in WAL mode and the WAL file currently contains one or more
** frames, return the size in bytes of the page images stored within the
** WAL frames. Otherwise, if this is not a WAL database or the WAL file
** is empty, return 0.
*/
int sqlite3PagerWalFramesize(Pager *pPager){
assert( pPager->eState>=PAGER_READER );
return sqlite3WalFramesize(pPager->pWal);
}
#endif
#if defined(SQLITE_USE_SEH) && !defined(SQLITE_OMIT_WAL)
int sqlite3PagerWalSystemErrno(Pager *pPager){
return sqlite3WalSystemErrno(pPager->pWal);
}
#endif
#endif /* SQLITE_OMIT_DISKIO */
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