mirror of
https://github.com/sqlite/sqlite.git
synced 2024-11-25 08:59:33 +01:00
235 lines
7.5 KiB
C
235 lines
7.5 KiB
C
/*
|
|
** 2013-10-01
|
|
**
|
|
** 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 program implements a high-speed version of the VACUUM command.
|
|
** It repacks an SQLite database to remove as much unused space as
|
|
** possible and to relocate content sequentially in the file.
|
|
**
|
|
** This program runs faster and uses less temporary disk space than the
|
|
** built-in VACUUM command. On the other hand, this program has a number
|
|
** of important restrictions relative to the built-in VACUUM command.
|
|
**
|
|
** (1) The caller must ensure that no other processes are accessing the
|
|
** database file while the vacuum is taking place. The usual SQLite
|
|
** file locking is insufficient for this. The caller must use
|
|
** external means to make sure only this one routine is reading and
|
|
** writing the database.
|
|
**
|
|
** (2) Database reconfiguration such as page size or auto_vacuum changes
|
|
** are not supported by this utility.
|
|
**
|
|
** (3) The database file might be renamed if a power loss or crash
|
|
** occurs at just the wrong moment. Recovery must be prepared to
|
|
** to deal with the possibly changed filename.
|
|
**
|
|
** This program is intended as a *Demonstration Only*. The intent of this
|
|
** program is to provide example code that application developers can use
|
|
** when creating similar functionality in their applications.
|
|
**
|
|
** To compile this program:
|
|
**
|
|
** cc fast_vacuum.c sqlite3.c
|
|
**
|
|
** Add whatever linker options are required. (Example: "-ldl -lpthread").
|
|
** Then to run the program:
|
|
**
|
|
** ./a.out file-to-vacuum
|
|
**
|
|
*/
|
|
#include "sqlite3.h"
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
|
|
/*
|
|
** Finalize a prepared statement. If an error has occurred, print the
|
|
** error message and exit.
|
|
*/
|
|
static void vacuumFinalize(sqlite3_stmt *pStmt){
|
|
sqlite3 *db = sqlite3_db_handle(pStmt);
|
|
int rc = sqlite3_finalize(pStmt);
|
|
if( rc ){
|
|
fprintf(stderr, "finalize error: %s\n", sqlite3_errmsg(db));
|
|
exit(1);
|
|
}
|
|
}
|
|
|
|
/*
|
|
** Execute zSql on database db. The SQL text is printed to standard
|
|
** output. If an error occurs, print an error message and exit the
|
|
** process.
|
|
*/
|
|
static void execSql(sqlite3 *db, const char *zSql){
|
|
sqlite3_stmt *pStmt;
|
|
if( !zSql ){
|
|
fprintf(stderr, "out of memory!\n");
|
|
exit(1);
|
|
}
|
|
printf("%s;\n", zSql);
|
|
if( SQLITE_OK!=sqlite3_prepare(db, zSql, -1, &pStmt, 0) ){
|
|
fprintf(stderr, "Error: %s\n", sqlite3_errmsg(db));
|
|
exit(1);
|
|
}
|
|
sqlite3_step(pStmt);
|
|
vacuumFinalize(pStmt);
|
|
}
|
|
|
|
/*
|
|
** Execute zSql on database db. The zSql statement returns exactly
|
|
** one column. Execute this return value as SQL on the same database.
|
|
**
|
|
** The zSql statement is printed on standard output prior to being
|
|
** run. If any errors occur, an error is printed and the process
|
|
** exits.
|
|
*/
|
|
static void execExecSql(sqlite3 *db, const char *zSql){
|
|
sqlite3_stmt *pStmt;
|
|
int rc;
|
|
|
|
printf("%s;\n", zSql);
|
|
rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0);
|
|
if( rc!=SQLITE_OK ){
|
|
fprintf(stderr, "Error: %s\n", sqlite3_errmsg(db));
|
|
exit(1);
|
|
}
|
|
while( SQLITE_ROW==sqlite3_step(pStmt) ){
|
|
execSql(db, (char*)sqlite3_column_text(pStmt, 0));
|
|
}
|
|
vacuumFinalize(pStmt);
|
|
}
|
|
|
|
|
|
int main(int argc, char **argv){
|
|
sqlite3 *db; /* Connection to the database file */
|
|
int rc; /* Return code from SQLite interface calls */
|
|
sqlite3_uint64 r; /* A random number */
|
|
const char *zDbToVacuum; /* Database to be vacuumed */
|
|
char *zBackupDb; /* Backup copy of the original database */
|
|
char *zTempDb; /* Temporary database */
|
|
char *zSql; /* An SQL statement */
|
|
|
|
if( argc!=2 ){
|
|
fprintf(stderr, "Usage: %s DATABASE\n", argv[0]);
|
|
return 1;
|
|
}
|
|
|
|
/* Identify the database file to be vacuumed and open it.
|
|
*/
|
|
zDbToVacuum = argv[1];
|
|
printf("-- open database file \"%s\"\n", zDbToVacuum);
|
|
rc = sqlite3_open(zDbToVacuum, &db);
|
|
if( rc ){
|
|
fprintf(stderr, "%s: %s\n", zDbToVacuum, sqlite3_errstr(rc));
|
|
return 1;
|
|
}
|
|
|
|
/* Create names for two other files. zTempDb will be a new database
|
|
** into which we construct a vacuumed copy of zDbToVacuum. zBackupDb
|
|
** will be a new name for zDbToVacuum after it is vacuumed.
|
|
*/
|
|
sqlite3_randomness(sizeof(r), &r);
|
|
zTempDb = sqlite3_mprintf("%s-vacuum-%016llx", zDbToVacuum, r);
|
|
zBackupDb = sqlite3_mprintf("%s-backup-%016llx", zDbToVacuum, r);
|
|
|
|
/* Attach the zTempDb database to the database connection.
|
|
*/
|
|
zSql = sqlite3_mprintf("ATTACH '%q' AS vacuum_db;", zTempDb);
|
|
execSql(db, zSql);
|
|
sqlite3_free(zSql);
|
|
|
|
/* TODO:
|
|
** Set the page_size and auto_vacuum mode for zTempDb here, if desired.
|
|
*/
|
|
|
|
/* The vacuum will occur inside of a transaction. Set writable_schema
|
|
** to ON so that we can directly update the sqlite_schema table in the
|
|
** zTempDb database.
|
|
*/
|
|
execSql(db, "PRAGMA writable_schema=ON");
|
|
execSql(db, "BEGIN");
|
|
|
|
|
|
/* Query the schema of the main database. Create a mirror schema
|
|
** in the temporary database.
|
|
*/
|
|
execExecSql(db,
|
|
"SELECT 'CREATE TABLE vacuum_db.' || substr(sql,14) "
|
|
" FROM sqlite_schema WHERE type='table' AND name!='sqlite_sequence'"
|
|
" AND rootpage>0"
|
|
);
|
|
execExecSql(db,
|
|
"SELECT 'CREATE INDEX vacuum_db.' || substr(sql,14)"
|
|
" FROM sqlite_schema WHERE sql LIKE 'CREATE INDEX %'"
|
|
);
|
|
execExecSql(db,
|
|
"SELECT 'CREATE UNIQUE INDEX vacuum_db.' || substr(sql,21) "
|
|
" FROM sqlite_schema WHERE sql LIKE 'CREATE UNIQUE INDEX %'"
|
|
);
|
|
|
|
/* Loop through the tables in the main database. For each, do
|
|
** an "INSERT INTO vacuum_db.xxx SELECT * FROM main.xxx;" to copy
|
|
** the contents to the temporary database.
|
|
*/
|
|
execExecSql(db,
|
|
"SELECT 'INSERT INTO vacuum_db.' || quote(name) "
|
|
"|| ' SELECT * FROM main.' || quote(name) "
|
|
"FROM main.sqlite_schema "
|
|
"WHERE type = 'table' AND name!='sqlite_sequence' "
|
|
" AND rootpage>0"
|
|
);
|
|
|
|
/* Copy over the sequence table
|
|
*/
|
|
execExecSql(db,
|
|
"SELECT 'DELETE FROM vacuum_db.' || quote(name) "
|
|
"FROM vacuum_db.sqlite_schema WHERE name='sqlite_sequence'"
|
|
);
|
|
execExecSql(db,
|
|
"SELECT 'INSERT INTO vacuum_db.' || quote(name) "
|
|
"|| ' SELECT * FROM main.' || quote(name) "
|
|
"FROM vacuum_db.sqlite_schema WHERE name=='sqlite_sequence'"
|
|
);
|
|
|
|
/* Copy the triggers, views, and virtual tables from the main database
|
|
** over to the temporary database. None of these objects has any
|
|
** associated storage, so all we have to do is copy their entries
|
|
** from the SQLITE_MASTER table.
|
|
*/
|
|
execSql(db,
|
|
"INSERT INTO vacuum_db.sqlite_schema "
|
|
" SELECT type, name, tbl_name, rootpage, sql"
|
|
" FROM main.sqlite_schema"
|
|
" WHERE type='view' OR type='trigger'"
|
|
" OR (type='table' AND rootpage=0)"
|
|
);
|
|
|
|
/* Commit the transaction and close the database
|
|
*/
|
|
execSql(db, "COMMIT");
|
|
printf("-- close database\n");
|
|
sqlite3_close(db);
|
|
|
|
|
|
/* At this point, zDbToVacuum is unchanged. zTempDb contains a
|
|
** vacuumed copy of zDbToVacuum. Rearrange filenames so that
|
|
** zTempDb becomes thenew zDbToVacuum.
|
|
*/
|
|
printf("-- rename \"%s\" to \"%s\"\n", zDbToVacuum, zBackupDb);
|
|
rename(zDbToVacuum, zBackupDb);
|
|
printf("-- rename \"%s\" to \"%s\"\n", zTempDb, zDbToVacuum);
|
|
rename(zTempDb, zDbToVacuum);
|
|
|
|
/* Release allocated memory */
|
|
sqlite3_free(zTempDb);
|
|
sqlite3_free(zBackupDb);
|
|
return 0;
|
|
}
|