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sqlite/ext/misc/stmt.c
drh 1935887a68 Ensure that all fields of static sqlite3_module objects are explicitly 
initialized, in order to hush-up nuisance compiler warnings.

FossilOrigin-Name: f3b3d712d6e58b1cb8fdebd2b6b3125080b6b3ac8c7c849a8cc1e5e778d62fe7
2023-10-06 12:51:05 +00:00

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/*
** 2017-05-31
**
** 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 file demonstrates an eponymous virtual table that returns information
** about all prepared statements for the database connection.
**
** Usage example:
**
** .load ./stmt
** .mode line
** .header on
** SELECT * FROM stmt;
*/
#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_STMTVTAB)
#if !defined(SQLITEINT_H)
#include "sqlite3ext.h"
#endif
SQLITE_EXTENSION_INIT1
#include <assert.h>
#include <string.h>
#ifndef SQLITE_OMIT_VIRTUALTABLE
#define STMT_NUM_INTEGER_COLUMN 10
typedef struct StmtRow StmtRow;
struct StmtRow {
sqlite3_int64 iRowid; /* Rowid value */
char *zSql; /* column "sql" */
int aCol[STMT_NUM_INTEGER_COLUMN+1]; /* all other column values */
StmtRow *pNext; /* Next row to return */
};
/* stmt_vtab is a subclass of sqlite3_vtab which will
** serve as the underlying representation of a stmt virtual table
*/
typedef struct stmt_vtab stmt_vtab;
struct stmt_vtab {
sqlite3_vtab base; /* Base class - must be first */
sqlite3 *db; /* Database connection for this stmt vtab */
};
/* stmt_cursor is a subclass of sqlite3_vtab_cursor which will
** serve as the underlying representation of a cursor that scans
** over rows of the result
*/
typedef struct stmt_cursor stmt_cursor;
struct stmt_cursor {
sqlite3_vtab_cursor base; /* Base class - must be first */
sqlite3 *db; /* Database connection for this cursor */
StmtRow *pRow; /* Current row */
};
/*
** The stmtConnect() method is invoked to create a new
** stmt_vtab that describes the stmt virtual table.
**
** Think of this routine as the constructor for stmt_vtab objects.
**
** All this routine needs to do is:
**
** (1) Allocate the stmt_vtab object and initialize all fields.
**
** (2) Tell SQLite (via the sqlite3_declare_vtab() interface) what the
** result set of queries against stmt will look like.
*/
static int stmtConnect(
sqlite3 *db,
void *pAux,
int argc, const char *const*argv,
sqlite3_vtab **ppVtab,
char **pzErr
){
stmt_vtab *pNew;
int rc;
/* Column numbers */
#define STMT_COLUMN_SQL 0 /* SQL for the statement */
#define STMT_COLUMN_NCOL 1 /* Number of result columns */
#define STMT_COLUMN_RO 2 /* True if read-only */
#define STMT_COLUMN_BUSY 3 /* True if currently busy */
#define STMT_COLUMN_NSCAN 4 /* SQLITE_STMTSTATUS_FULLSCAN_STEP */
#define STMT_COLUMN_NSORT 5 /* SQLITE_STMTSTATUS_SORT */
#define STMT_COLUMN_NAIDX 6 /* SQLITE_STMTSTATUS_AUTOINDEX */
#define STMT_COLUMN_NSTEP 7 /* SQLITE_STMTSTATUS_VM_STEP */
#define STMT_COLUMN_REPREP 8 /* SQLITE_STMTSTATUS_REPREPARE */
#define STMT_COLUMN_RUN 9 /* SQLITE_STMTSTATUS_RUN */
#define STMT_COLUMN_MEM 10 /* SQLITE_STMTSTATUS_MEMUSED */
(void)pAux;
(void)argc;
(void)argv;
(void)pzErr;
rc = sqlite3_declare_vtab(db,
"CREATE TABLE x(sql,ncol,ro,busy,nscan,nsort,naidx,nstep,"
"reprep,run,mem)");
if( rc==SQLITE_OK ){
pNew = sqlite3_malloc64( sizeof(*pNew) );
*ppVtab = (sqlite3_vtab*)pNew;
if( pNew==0 ) return SQLITE_NOMEM;
memset(pNew, 0, sizeof(*pNew));
pNew->db = db;
}
return rc;
}
/*
** This method is the destructor for stmt_cursor objects.
*/
static int stmtDisconnect(sqlite3_vtab *pVtab){
sqlite3_free(pVtab);
return SQLITE_OK;
}
/*
** Constructor for a new stmt_cursor object.
*/
static int stmtOpen(sqlite3_vtab *p, sqlite3_vtab_cursor **ppCursor){
stmt_cursor *pCur;
pCur = sqlite3_malloc64( sizeof(*pCur) );
if( pCur==0 ) return SQLITE_NOMEM;
memset(pCur, 0, sizeof(*pCur));
pCur->db = ((stmt_vtab*)p)->db;
*ppCursor = &pCur->base;
return SQLITE_OK;
}
static void stmtCsrReset(stmt_cursor *pCur){
StmtRow *pRow = 0;
StmtRow *pNext = 0;
for(pRow=pCur->pRow; pRow; pRow=pNext){
pNext = pRow->pNext;
sqlite3_free(pRow);
}
pCur->pRow = 0;
}
/*
** Destructor for a stmt_cursor.
*/
static int stmtClose(sqlite3_vtab_cursor *cur){
stmtCsrReset((stmt_cursor*)cur);
sqlite3_free(cur);
return SQLITE_OK;
}
/*
** Advance a stmt_cursor to its next row of output.
*/
static int stmtNext(sqlite3_vtab_cursor *cur){
stmt_cursor *pCur = (stmt_cursor*)cur;
StmtRow *pNext = pCur->pRow->pNext;
sqlite3_free(pCur->pRow);
pCur->pRow = pNext;
return SQLITE_OK;
}
/*
** Return values of columns for the row at which the stmt_cursor
** is currently pointing.
*/
static int stmtColumn(
sqlite3_vtab_cursor *cur, /* The cursor */
sqlite3_context *ctx, /* First argument to sqlite3_result_...() */
int i /* Which column to return */
){
stmt_cursor *pCur = (stmt_cursor*)cur;
StmtRow *pRow = pCur->pRow;
if( i==STMT_COLUMN_SQL ){
sqlite3_result_text(ctx, pRow->zSql, -1, SQLITE_TRANSIENT);
}else{
sqlite3_result_int(ctx, pRow->aCol[i]);
}
return SQLITE_OK;
}
/*
** Return the rowid for the current row. In this implementation, the
** rowid is the same as the output value.
*/
static int stmtRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
stmt_cursor *pCur = (stmt_cursor*)cur;
*pRowid = pCur->pRow->iRowid;
return SQLITE_OK;
}
/*
** Return TRUE if the cursor has been moved off of the last
** row of output.
*/
static int stmtEof(sqlite3_vtab_cursor *cur){
stmt_cursor *pCur = (stmt_cursor*)cur;
return pCur->pRow==0;
}
/*
** This method is called to "rewind" the stmt_cursor object back
** to the first row of output. This method is always called at least
** once prior to any call to stmtColumn() or stmtRowid() or
** stmtEof().
*/
static int stmtFilter(
sqlite3_vtab_cursor *pVtabCursor,
int idxNum, const char *idxStr,
int argc, sqlite3_value **argv
){
stmt_cursor *pCur = (stmt_cursor *)pVtabCursor;
sqlite3_stmt *p = 0;
sqlite3_int64 iRowid = 1;
StmtRow **ppRow = 0;
(void)idxNum;
(void)idxStr;
(void)argc;
(void)argv;
stmtCsrReset(pCur);
ppRow = &pCur->pRow;
for(p=sqlite3_next_stmt(pCur->db, 0); p; p=sqlite3_next_stmt(pCur->db, p)){
const char *zSql = sqlite3_sql(p);
sqlite3_int64 nSql = zSql ? strlen(zSql)+1 : 0;
StmtRow *pNew = (StmtRow*)sqlite3_malloc64(sizeof(StmtRow) + nSql);
if( pNew==0 ) return SQLITE_NOMEM;
memset(pNew, 0, sizeof(StmtRow));
if( zSql ){
pNew->zSql = (char*)&pNew[1];
memcpy(pNew->zSql, zSql, nSql);
}
pNew->aCol[STMT_COLUMN_NCOL] = sqlite3_column_count(p);
pNew->aCol[STMT_COLUMN_RO] = sqlite3_stmt_readonly(p);
pNew->aCol[STMT_COLUMN_BUSY] = sqlite3_stmt_busy(p);
pNew->aCol[STMT_COLUMN_NSCAN] = sqlite3_stmt_status(
p, SQLITE_STMTSTATUS_FULLSCAN_STEP, 0
);
pNew->aCol[STMT_COLUMN_NSORT] = sqlite3_stmt_status(
p, SQLITE_STMTSTATUS_SORT, 0
);
pNew->aCol[STMT_COLUMN_NAIDX] = sqlite3_stmt_status(
p, SQLITE_STMTSTATUS_AUTOINDEX, 0
);
pNew->aCol[STMT_COLUMN_NSTEP] = sqlite3_stmt_status(
p, SQLITE_STMTSTATUS_VM_STEP, 0
);
pNew->aCol[STMT_COLUMN_REPREP] = sqlite3_stmt_status(
p, SQLITE_STMTSTATUS_REPREPARE, 0
);
pNew->aCol[STMT_COLUMN_RUN] = sqlite3_stmt_status(
p, SQLITE_STMTSTATUS_RUN, 0
);
pNew->aCol[STMT_COLUMN_MEM] = sqlite3_stmt_status(
p, SQLITE_STMTSTATUS_MEMUSED, 0
);
pNew->iRowid = iRowid++;
*ppRow = pNew;
ppRow = &pNew->pNext;
}
return SQLITE_OK;
}
/*
** SQLite will invoke this method one or more times while planning a query
** that uses the stmt virtual table. This routine needs to create
** a query plan for each invocation and compute an estimated cost for that
** plan.
*/
static int stmtBestIndex(
sqlite3_vtab *tab,
sqlite3_index_info *pIdxInfo
){
(void)tab;
pIdxInfo->estimatedCost = (double)500;
pIdxInfo->estimatedRows = 500;
return SQLITE_OK;
}
/*
** This following structure defines all the methods for the
** stmt virtual table.
*/
static sqlite3_module stmtModule = {
0, /* iVersion */
0, /* xCreate */
stmtConnect, /* xConnect */
stmtBestIndex, /* xBestIndex */
stmtDisconnect, /* xDisconnect */
0, /* xDestroy */
stmtOpen, /* xOpen - open a cursor */
stmtClose, /* xClose - close a cursor */
stmtFilter, /* xFilter - configure scan constraints */
stmtNext, /* xNext - advance a cursor */
stmtEof, /* xEof - check for end of scan */
stmtColumn, /* xColumn - read data */
stmtRowid, /* xRowid - read data */
0, /* xUpdate */
0, /* xBegin */
0, /* xSync */
0, /* xCommit */
0, /* xRollback */
0, /* xFindMethod */
0, /* xRename */
0, /* xSavepoint */
0, /* xRelease */
0, /* xRollbackTo */
0, /* xShadowName */
0 /* xIntegrity */
};
#endif /* SQLITE_OMIT_VIRTUALTABLE */
int sqlite3StmtVtabInit(sqlite3 *db){
int rc = SQLITE_OK;
#ifndef SQLITE_OMIT_VIRTUALTABLE
rc = sqlite3_create_module(db, "sqlite_stmt", &stmtModule, 0);
#endif
return rc;
}
#ifndef SQLITE_CORE
#ifdef _WIN32
__declspec(dllexport)
#endif
int sqlite3_stmt_init(
sqlite3 *db,
char **pzErrMsg,
const sqlite3_api_routines *pApi
){
int rc = SQLITE_OK;
SQLITE_EXTENSION_INIT2(pApi);
#ifndef SQLITE_OMIT_VIRTUALTABLE
rc = sqlite3StmtVtabInit(db);
#endif
return rc;
}
#endif /* SQLITE_CORE */
#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_STMTVTAB) */
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