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/*
** 2003 April 6
**
** 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 contains code used to implement the VACUUM command.
**
** Most of the code in this file may be omitted by defining the
** SQLITE_OMIT_VACUUM macro.
**
** $Id$
*/
#include "sqliteInt.h"
#include "os.h"
#if !defined(SQLITE_OMIT_VACUUM) || SQLITE_OMIT_VACUUM
/*
** Generate a random name of 20 character in length.
*/
static void randomName(unsigned char *zBuf){
static const unsigned char zChars[] =
"abcdefghijklmnopqrstuvwxyz"
"0123456789";
int i;
sqlite3Randomness(20, zBuf);
for(i=0; i<20; i++){
zBuf[i] = zChars[ zBuf[i]%(sizeof(zChars)-1) ];
}
}
/*
** Execute zSql on database db. Return an error code.
*/
static int execSql(sqlite3 *db, const char *zSql){
sqlite3_stmt *pStmt;
if( SQLITE_OK!=sqlite3_prepare(db, zSql, -1, &pStmt, 0) ){
return sqlite3_errcode(db);
}
while( SQLITE_ROW==sqlite3_step(pStmt) );
return sqlite3_finalize(pStmt);
}
/*
** Execute zSql on database db. The statement returns exactly
** one column. Execute this as SQL on the same database.
*/
static int execExecSql(sqlite3 *db, const char *zSql){
sqlite3_stmt *pStmt;
int rc;
rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0);
if( rc!=SQLITE_OK ) return rc;
while( SQLITE_ROW==sqlite3_step(pStmt) ){
rc = execSql(db, sqlite3_column_text(pStmt, 0));
if( rc!=SQLITE_OK ){
sqlite3_finalize(pStmt);
return rc;
}
}
return sqlite3_finalize(pStmt);
}
#endif
/*
** The non-standard VACUUM command is used to clean up the database,
** collapse free space, etc. It is modelled after the VACUUM command
** in PostgreSQL.
**
** In version 1.0.x of SQLite, the VACUUM command would call
** gdbm_reorganize() on all the database tables. But beginning
** with 2.0.0, SQLite no longer uses GDBM so this command has
** become a no-op.
*/
void sqlite3Vacuum(Parse *pParse, Token *pTableName){
Vdbe *v = sqlite3GetVdbe(pParse);
if( v ){
sqlite3VdbeAddOp(v, OP_Vacuum, 0, 0);
}
return;
}
/*
** This routine implements the OP_Vacuum opcode of the VDBE.
*/
int sqlite3RunVacuum(char **pzErrMsg, sqlite3 *db){
int rc = SQLITE_OK; /* Return code from service routines */
#if !defined(SQLITE_OMIT_VACUUM) || SQLITE_OMIT_VACUUM
const char *zFilename; /* full pathname of the database file */
int nFilename; /* number of characters in zFilename[] */
char *zTemp = 0; /* a temporary file in same directory as zFilename */
int i; /* Loop counter */
Btree *pMain; /* The database being vacuumed */
Btree *pTemp;
char *zSql = 0;
if( !db->autoCommit ){
sqlite3SetString(pzErrMsg, "cannot VACUUM from within a transaction",
(char*)0);
rc = SQLITE_ERROR;
goto end_of_vacuum;
}
/* Get the full pathname of the database file and create a
** temporary filename in the same directory as the original file.
*/
pMain = db->aDb[0].pBt;
zFilename = sqlite3BtreeGetFilename(pMain);
assert( zFilename );
if( zFilename[0]=='\0' ){
/* The in-memory database. Do nothing. Return directly to avoid causing
** an error trying to DETACH the vacuum_db (which never got attached)
** in the exit-handler.
*/
return SQLITE_OK;
}
nFilename = strlen(zFilename);
zTemp = sqliteMalloc( nFilename+100 );
if( zTemp==0 ){
rc = SQLITE_NOMEM;
goto end_of_vacuum;
}
strcpy(zTemp, zFilename);
i = 0;
do {
zTemp[nFilename] = '-';
randomName((unsigned char*)&zTemp[nFilename+1]);
} while( i<10 && sqlite3OsFileExists(zTemp) );
/* Attach the temporary database as 'vacuum_db'. The synchronous pragma
** can be set to 'off' for this file, as it is not recovered if a crash
** occurs anyway. The integrity of the database is maintained by a
** (possibly synchronous) transaction opened on the main database before
** sqlite3BtreeCopyFile() is called.
**
** An optimisation would be to use a non-journaled pager.
*/
zSql = sqlite3MPrintf("ATTACH '%q' AS vacuum_db;", zTemp);
if( !zSql ){
rc = SQLITE_NOMEM;
goto end_of_vacuum;
}
rc = execSql(db, zSql);
sqliteFree(zSql);
zSql = 0;
if( rc!=SQLITE_OK ) goto end_of_vacuum;
assert( strcmp(db->aDb[db->nDb-1].zName,"vacuum_db")==0 );
pTemp = db->aDb[db->nDb-1].pBt;
sqlite3BtreeSetPageSize(pTemp, sqlite3BtreeGetPageSize(pMain),
sqlite3BtreeGetReserve(pMain));
assert( sqlite3BtreeGetPageSize(pTemp)==sqlite3BtreeGetPageSize(pMain) );
execSql(db, "PRAGMA vacuum_db.synchronous=OFF");
/* Begin a transaction */
rc = execSql(db, "BEGIN;");
if( rc!=SQLITE_OK ) goto end_of_vacuum;
/* Query the schema of the main database. Create a mirror schema
** in the temporary database.
*/
rc = execExecSql(db,
"SELECT 'CREATE TABLE vacuum_db.' || substr(sql,14,100000000) "
" FROM sqlite_master WHERE type='table' "
"UNION ALL "
"SELECT 'CREATE INDEX vacuum_db.' || substr(sql,14,100000000) "
" FROM sqlite_master WHERE sql LIKE 'CREATE INDEX %' "
"UNION ALL "
"SELECT 'CREATE UNIQUE INDEX vacuum_db.' || substr(sql,21,100000000) "
" FROM sqlite_master WHERE sql LIKE 'CREATE UNIQUE INDEX %'"
"UNION ALL "
"SELECT 'CREATE VIEW vacuum_db.' || substr(sql,13,100000000) "
" FROM sqlite_master WHERE type='view'"
);
if( rc!=SQLITE_OK ) goto end_of_vacuum;
/* Loop through the tables in the main database. For each, do
** an "INSERT INTO vacuum_db.xxx SELECT * FROM xxx;" to copy
** the contents to the temporary database.
*/
rc = execExecSql(db,
"SELECT 'INSERT INTO vacuum_db.' || quote(name) "
"|| ' SELECT * FROM ' || quote(name) || ';'"
"FROM sqlite_master "
"WHERE type = 'table';"
);
if( rc!=SQLITE_OK ) goto end_of_vacuum;
/* Copy the triggers from the main database to the temporary database.
** This was deferred before in case the triggers interfered with copying
** the data. It's possible the indices should be deferred until this
** point also.
*/
rc = execExecSql(db,
"SELECT 'CREATE TRIGGER vacuum_db.' || substr(sql, 16, 1000000) "
"FROM sqlite_master WHERE type='trigger'"
);
if( rc!=SQLITE_OK ) goto end_of_vacuum;
/* At this point, unless the main db was completely empty, there is now a
** transaction open on the vacuum database, but not on the main database.
** Open a btree level transaction on the main database. This allows a
** call to sqlite3BtreeCopyFile(). The main database btree level
** transaction is then committed, so the SQL level never knows it was
** opened for writing. This way, the SQL transaction used to create the
** temporary database never needs to be committed.
*/
if( sqlite3BtreeIsInTrans(pTemp) ){
u32 meta;
assert( 0==sqlite3BtreeIsInTrans(pMain) );
rc = sqlite3BtreeBeginTrans(pMain, 1);
if( rc!=SQLITE_OK ) goto end_of_vacuum;
/* Copy Btree meta values 3 and 4. These correspond to SQL layer meta
** values 2 and 3, the default values of a couple of pragmas.
*/
rc = sqlite3BtreeGetMeta(pMain, 3, &meta);
if( rc!=SQLITE_OK ) goto end_of_vacuum;
rc = sqlite3BtreeUpdateMeta(pTemp, 3, meta);
if( rc!=SQLITE_OK ) goto end_of_vacuum;
rc = sqlite3BtreeGetMeta(pMain, 4, &meta);
if( rc!=SQLITE_OK ) goto end_of_vacuum;
rc = sqlite3BtreeUpdateMeta(pTemp, 4, meta);
if( rc!=SQLITE_OK ) goto end_of_vacuum;
rc = sqlite3BtreeCopyFile(pMain, pTemp);
if( rc!=SQLITE_OK ) goto end_of_vacuum;
rc = sqlite3BtreeCommit(pMain);
}
end_of_vacuum:
/* Currently there is an SQL level transaction open on the vacuum
** database. No locks are held on any other files (since the main file
** was committed at the btree level). So it safe to end the transaction
** by manually setting the autoCommit flag to true and detaching the
** vacuum database. The vacuum_db journal file is deleted when the pager
** is closed by the DETACH.
*/
db->autoCommit = 1;
if( rc==SQLITE_OK ){
rc = execSql(db, "DETACH vacuum_db;");
}else{
execSql(db, "DETACH vacuum_db;");
}
if( zTemp ){
sqlite3OsDelete(zTemp);
sqliteFree(zTemp);
}
if( zSql ) sqliteFree( zSql );
sqlite3ResetInternalSchema(db, 0);
#endif
return rc;
}
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