/*
** 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
/* 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 */
sqlite3_stmt *pStmt; /* Statement cursor is currently pointing at */
sqlite3_int64 iRowid; /* The rowid */
};
/*
** 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 */
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_malloc( 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_malloc( 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;
}
/*
** Destructor for a stmt_cursor.
*/
static int stmtClose(sqlite3_vtab_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;
pCur->iRowid++;
pCur->pStmt = sqlite3_next_stmt(pCur->db, pCur->pStmt);
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;
switch( i ){
case STMT_COLUMN_SQL: {
sqlite3_result_text(ctx, sqlite3_sql(pCur->pStmt), -1, SQLITE_TRANSIENT);
break;
}
case STMT_COLUMN_NCOL: {
sqlite3_result_int(ctx, sqlite3_column_count(pCur->pStmt));
break;
}
case STMT_COLUMN_RO: {
sqlite3_result_int(ctx, sqlite3_stmt_readonly(pCur->pStmt));
break;
}
case STMT_COLUMN_BUSY: {
sqlite3_result_int(ctx, sqlite3_stmt_busy(pCur->pStmt));
break;
}
case STMT_COLUMN_MEM: {
i = SQLITE_STMTSTATUS_MEMUSED +
STMT_COLUMN_NSCAN - SQLITE_STMTSTATUS_FULLSCAN_STEP;
/* Fall thru */
}
case STMT_COLUMN_NSCAN:
case STMT_COLUMN_NSORT:
case STMT_COLUMN_NAIDX:
case STMT_COLUMN_NSTEP:
case STMT_COLUMN_REPREP:
case STMT_COLUMN_RUN: {
sqlite3_result_int(ctx, sqlite3_stmt_status(pCur->pStmt,
i-STMT_COLUMN_NSCAN+SQLITE_STMTSTATUS_FULLSCAN_STEP, 0));
break;
}
}
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->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->pStmt==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;
pCur->pStmt = 0;
pCur->iRowid = 0;
return stmtNext(pVtabCursor);
}
/*
** 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
){
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 */
};
#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) */