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authorHans-Christoph Steiner <hans@eds.org>2012-03-30 20:42:12 -0400
committerHans-Christoph Steiner <hans@eds.org>2012-03-30 20:42:12 -0400
commit7bb481fda9ecb134804b49c2ce77ca28f7eea583 (patch)
tree31b520b9914d3e2453968abe375f2c102772c3dc /src/vacuum.c
Imported Upstream version 2.0.3
Diffstat (limited to 'src/vacuum.c')
-rw-r--r--src/vacuum.c343
1 files changed, 343 insertions, 0 deletions
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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.
+*/
+#include "sqliteInt.h"
+#include "vdbeInt.h"
+
+#if !defined(SQLITE_OMIT_VACUUM) && !defined(SQLITE_OMIT_ATTACH)
+/*
+** Finalize a prepared statement. If there was an error, store the
+** text of the error message in *pzErrMsg. Return the result code.
+*/
+static int vacuumFinalize(sqlite3 *db, sqlite3_stmt *pStmt, char **pzErrMsg){
+ int rc;
+ rc = sqlite3VdbeFinalize((Vdbe*)pStmt);
+ if( rc ){
+ sqlite3SetString(pzErrMsg, db, sqlite3_errmsg(db));
+ }
+ return rc;
+}
+
+/*
+** Execute zSql on database db. Return an error code.
+*/
+static int execSql(sqlite3 *db, char **pzErrMsg, const char *zSql){
+ sqlite3_stmt *pStmt;
+ VVA_ONLY( int rc; )
+ if( !zSql ){
+ return SQLITE_NOMEM;
+ }
+ if( SQLITE_OK!=sqlite3_prepare(db, zSql, -1, &pStmt, 0) ){
+ sqlite3SetString(pzErrMsg, db, sqlite3_errmsg(db));
+ return sqlite3_errcode(db);
+ }
+ VVA_ONLY( rc = ) sqlite3_step(pStmt);
+ assert( rc!=SQLITE_ROW || (db->flags&SQLITE_CountRows) );
+ return vacuumFinalize(db, pStmt, pzErrMsg);
+}
+
+/*
+** Execute zSql on database db. The statement returns exactly
+** one column. Execute this as SQL on the same database.
+*/
+static int execExecSql(sqlite3 *db, char **pzErrMsg, 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, pzErrMsg, (char*)sqlite3_column_text(pStmt, 0));
+ if( rc!=SQLITE_OK ){
+ vacuumFinalize(db, pStmt, pzErrMsg);
+ return rc;
+ }
+ }
+
+ return vacuumFinalize(db, pStmt, pzErrMsg);
+}
+
+/*
+** 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){
+ Vdbe *v = sqlite3GetVdbe(pParse);
+ if( v ){
+ sqlite3VdbeAddOp2(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 */
+ Btree *pMain; /* The database being vacuumed */
+ Btree *pTemp; /* The temporary database we vacuum into */
+ char *zSql = 0; /* SQL statements */
+ int saved_flags; /* Saved value of the db->flags */
+ int saved_nChange; /* Saved value of db->nChange */
+ int saved_nTotalChange; /* Saved value of db->nTotalChange */
+ void (*saved_xTrace)(void*,const char*); /* Saved db->xTrace */
+ Db *pDb = 0; /* Database to detach at end of vacuum */
+ int isMemDb; /* True if vacuuming a :memory: database */
+ int nRes; /* Bytes of reserved space at the end of each page */
+ int nDb; /* Number of attached databases */
+
+ if( !db->autoCommit ){
+ sqlite3SetString(pzErrMsg, db, "cannot VACUUM from within a transaction");
+ return SQLITE_ERROR;
+ }
+ if( db->activeVdbeCnt>1 ){
+ sqlite3SetString(pzErrMsg, db,"cannot VACUUM - SQL statements in progress");
+ return SQLITE_ERROR;
+ }
+
+ /* Save the current value of the database flags so that it can be
+ ** restored before returning. Then set the writable-schema flag, and
+ ** disable CHECK and foreign key constraints. */
+ saved_flags = db->flags;
+ saved_nChange = db->nChange;
+ saved_nTotalChange = db->nTotalChange;
+ saved_xTrace = db->xTrace;
+ db->flags |= SQLITE_WriteSchema | SQLITE_IgnoreChecks | SQLITE_PreferBuiltin;
+ db->flags &= ~(SQLITE_ForeignKeys | SQLITE_ReverseOrder);
+ db->xTrace = 0;
+
+ pMain = db->aDb[0].pBt;
+ isMemDb = sqlite3PagerIsMemdb(sqlite3BtreePager(pMain));
+
+ /* 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.
+ ** (Later:) I tried setting "PRAGMA vacuum_db.journal_mode=OFF" but
+ ** that actually made the VACUUM run slower. Very little journalling
+ ** actually occurs when doing a vacuum since the vacuum_db is initially
+ ** empty. Only the journal header is written. Apparently it takes more
+ ** time to parse and run the PRAGMA to turn journalling off than it does
+ ** to write the journal header file.
+ */
+ nDb = db->nDb;
+ if( sqlite3TempInMemory(db) ){
+ zSql = "ATTACH ':memory:' AS vacuum_db;";
+ }else{
+ zSql = "ATTACH '' AS vacuum_db;";
+ }
+ rc = execSql(db, pzErrMsg, zSql);
+ if( db->nDb>nDb ){
+ pDb = &db->aDb[db->nDb-1];
+ assert( strcmp(pDb->zName,"vacuum_db")==0 );
+ }
+ if( rc!=SQLITE_OK ) goto end_of_vacuum;
+ pTemp = db->aDb[db->nDb-1].pBt;
+
+ /* The call to execSql() to attach the temp database has left the file
+ ** locked (as there was more than one active statement when the transaction
+ ** to read the schema was concluded. Unlock it here so that this doesn't
+ ** cause problems for the call to BtreeSetPageSize() below. */
+ sqlite3BtreeCommit(pTemp);
+
+ nRes = sqlite3BtreeGetReserve(pMain);
+
+ /* A VACUUM cannot change the pagesize of an encrypted database. */
+#ifdef SQLITE_HAS_CODEC
+ if( db->nextPagesize ){
+ extern void sqlite3CodecGetKey(sqlite3*, int, void**, int*);
+ int nKey;
+ char *zKey;
+ sqlite3CodecGetKey(db, 0, (void**)&zKey, &nKey);
+ if( nKey ) db->nextPagesize = 0;
+ }
+#endif
+
+ /* Do not attempt to change the page size for a WAL database */
+ if( sqlite3PagerGetJournalMode(sqlite3BtreePager(pMain))
+ ==PAGER_JOURNALMODE_WAL ){
+ db->nextPagesize = 0;
+ }
+
+ if( sqlite3BtreeSetPageSize(pTemp, sqlite3BtreeGetPageSize(pMain), nRes, 0)
+ || (!isMemDb && sqlite3BtreeSetPageSize(pTemp, db->nextPagesize, nRes, 0))
+ || NEVER(db->mallocFailed)
+ ){
+ rc = SQLITE_NOMEM;
+ goto end_of_vacuum;
+ }
+ rc = execSql(db, pzErrMsg, "PRAGMA vacuum_db.synchronous=OFF");
+ if( rc!=SQLITE_OK ){
+ goto end_of_vacuum;
+ }
+
+#ifndef SQLITE_OMIT_AUTOVACUUM
+ sqlite3BtreeSetAutoVacuum(pTemp, db->nextAutovac>=0 ? db->nextAutovac :
+ sqlite3BtreeGetAutoVacuum(pMain));
+#endif
+
+ /* Begin a transaction */
+ rc = execSql(db, pzErrMsg, "BEGIN EXCLUSIVE;");
+ 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, pzErrMsg,
+ "SELECT 'CREATE TABLE vacuum_db.' || substr(sql,14) "
+ " FROM sqlite_master WHERE type='table' AND name!='sqlite_sequence'"
+ " AND rootpage>0"
+ );
+ if( rc!=SQLITE_OK ) goto end_of_vacuum;
+ rc = execExecSql(db, pzErrMsg,
+ "SELECT 'CREATE INDEX vacuum_db.' || substr(sql,14)"
+ " FROM sqlite_master WHERE sql LIKE 'CREATE INDEX %' ");
+ if( rc!=SQLITE_OK ) goto end_of_vacuum;
+ rc = execExecSql(db, pzErrMsg,
+ "SELECT 'CREATE UNIQUE INDEX vacuum_db.' || substr(sql,21) "
+ " FROM sqlite_master WHERE sql LIKE 'CREATE UNIQUE INDEX %'");
+ 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 main.xxx;" to copy
+ ** the contents to the temporary database.
+ */
+ rc = execExecSql(db, pzErrMsg,
+ "SELECT 'INSERT INTO vacuum_db.' || quote(name) "
+ "|| ' SELECT * FROM main.' || quote(name) || ';'"
+ "FROM main.sqlite_master "
+ "WHERE type = 'table' AND name!='sqlite_sequence' "
+ " AND rootpage>0"
+ );
+ if( rc!=SQLITE_OK ) goto end_of_vacuum;
+
+ /* Copy over the sequence table
+ */
+ rc = execExecSql(db, pzErrMsg,
+ "SELECT 'DELETE FROM vacuum_db.' || quote(name) || ';' "
+ "FROM vacuum_db.sqlite_master WHERE name='sqlite_sequence' "
+ );
+ if( rc!=SQLITE_OK ) goto end_of_vacuum;
+ rc = execExecSql(db, pzErrMsg,
+ "SELECT 'INSERT INTO vacuum_db.' || quote(name) "
+ "|| ' SELECT * FROM main.' || quote(name) || ';' "
+ "FROM vacuum_db.sqlite_master WHERE name=='sqlite_sequence';"
+ );
+ if( rc!=SQLITE_OK ) goto end_of_vacuum;
+
+
+ /* 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.
+ */
+ rc = execSql(db, pzErrMsg,
+ "INSERT INTO vacuum_db.sqlite_master "
+ " SELECT type, name, tbl_name, rootpage, sql"
+ " FROM main.sqlite_master"
+ " WHERE type='view' OR type='trigger'"
+ " OR (type='table' AND rootpage=0)"
+ );
+ if( rc ) goto end_of_vacuum;
+
+ /* At this point, there is a write transaction open on both the
+ ** vacuum database and the main database. Assuming no error occurs,
+ ** both transactions are closed by this block - the main database
+ ** transaction by sqlite3BtreeCopyFile() and the other by an explicit
+ ** call to sqlite3BtreeCommit().
+ */
+ {
+ u32 meta;
+ int i;
+
+ /* This array determines which meta meta values are preserved in the
+ ** vacuum. Even entries are the meta value number and odd entries
+ ** are an increment to apply to the meta value after the vacuum.
+ ** The increment is used to increase the schema cookie so that other
+ ** connections to the same database will know to reread the schema.
+ */
+ static const unsigned char aCopy[] = {
+ BTREE_SCHEMA_VERSION, 1, /* Add one to the old schema cookie */
+ BTREE_DEFAULT_CACHE_SIZE, 0, /* Preserve the default page cache size */
+ BTREE_TEXT_ENCODING, 0, /* Preserve the text encoding */
+ BTREE_USER_VERSION, 0, /* Preserve the user version */
+ };
+
+ assert( 1==sqlite3BtreeIsInTrans(pTemp) );
+ assert( 1==sqlite3BtreeIsInTrans(pMain) );
+
+ /* Copy Btree meta values */
+ for(i=0; i<ArraySize(aCopy); i+=2){
+ /* GetMeta() and UpdateMeta() cannot fail in this context because
+ ** we already have page 1 loaded into cache and marked dirty. */
+ sqlite3BtreeGetMeta(pMain, aCopy[i], &meta);
+ rc = sqlite3BtreeUpdateMeta(pTemp, aCopy[i], meta+aCopy[i+1]);
+ if( NEVER(rc!=SQLITE_OK) ) goto end_of_vacuum;
+ }
+
+ rc = sqlite3BtreeCopyFile(pMain, pTemp);
+ if( rc!=SQLITE_OK ) goto end_of_vacuum;
+ rc = sqlite3BtreeCommit(pTemp);
+ if( rc!=SQLITE_OK ) goto end_of_vacuum;
+#ifndef SQLITE_OMIT_AUTOVACUUM
+ sqlite3BtreeSetAutoVacuum(pMain, sqlite3BtreeGetAutoVacuum(pTemp));
+#endif
+ }
+
+ assert( rc==SQLITE_OK );
+ rc = sqlite3BtreeSetPageSize(pMain, sqlite3BtreeGetPageSize(pTemp), nRes,1);
+
+end_of_vacuum:
+ /* Restore the original value of db->flags */
+ db->flags = saved_flags;
+ db->nChange = saved_nChange;
+ db->nTotalChange = saved_nTotalChange;
+ db->xTrace = saved_xTrace;
+ sqlite3BtreeSetPageSize(pMain, -1, -1, 1);
+
+ /* 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( pDb ){
+ sqlite3BtreeClose(pDb->pBt);
+ pDb->pBt = 0;
+ pDb->pSchema = 0;
+ }
+
+ /* This both clears the schemas and reduces the size of the db->aDb[]
+ ** array. */
+ sqlite3ResetInternalSchema(db, -1);
+
+ return rc;
+}
+
+#endif /* SQLITE_OMIT_VACUUM && SQLITE_OMIT_ATTACH */