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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)
+
+/*
+** Execute zSql on database db.
+**
+** If zSql returns rows, then each row will have exactly one
+** column. (This will only happen if zSql begins with "SELECT".)
+** Take each row of result and call execSql() again recursively.
+**
+** The execSqlF() routine does the same thing, except it accepts
+** a format string as its third argument
+*/
+static int execSql(sqlite3 *db, char **pzErrMsg, const char *zSql){
+ sqlite3_stmt *pStmt;
+ int rc;
+
+ /* printf("SQL: [%s]\n", zSql); fflush(stdout); */
+ rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
+ if( rc!=SQLITE_OK ) return rc;
+ while( SQLITE_ROW==(rc = sqlite3_step(pStmt)) ){
+ const char *zSubSql = (const char*)sqlite3_column_text(pStmt,0);
+ assert( sqlite3_strnicmp(zSql,"SELECT",6)==0 );
+ /* The secondary SQL must be one of CREATE TABLE, CREATE INDEX,
+ ** or INSERT. Historically there have been attacks that first
+ ** corrupt the sqlite_schema.sql field with other kinds of statements
+ ** then run VACUUM to get those statements to execute at inappropriate
+ ** times. */
+ if( zSubSql
+ && (strncmp(zSubSql,"CRE",3)==0 || strncmp(zSubSql,"INS",3)==0)
+ ){
+ rc = execSql(db, pzErrMsg, zSubSql);
+ if( rc!=SQLITE_OK ) break;
+ }
+ }
+ assert( rc!=SQLITE_ROW );
+ if( rc==SQLITE_DONE ) rc = SQLITE_OK;
+ if( rc ){
+ sqlite3SetString(pzErrMsg, db, sqlite3_errmsg(db));
+ }
+ (void)sqlite3_finalize(pStmt);
+ return rc;
+}
+static int execSqlF(sqlite3 *db, char **pzErrMsg, const char *zSql, ...){
+ char *z;
+ va_list ap;
+ int rc;
+ va_start(ap, zSql);
+ z = sqlite3VMPrintf(db, zSql, ap);
+ va_end(ap);
+ if( z==0 ) return SQLITE_NOMEM;
+ rc = execSql(db, pzErrMsg, z);
+ sqlite3DbFree(db, z);
+ return rc;
+}
+
+/*
+** The VACUUM command is used to clean up the database,
+** collapse free space, etc. It is modelled after the VACUUM command
+** in PostgreSQL. The VACUUM command works as follows:
+**
+** (1) Create a new transient database file
+** (2) Copy all content from the database being vacuumed into
+** the new transient database file
+** (3) Copy content from the transient database back into the
+** original database.
+**
+** The transient database requires temporary disk space approximately
+** equal to the size of the original database. The copy operation of
+** step (3) requires additional temporary disk space approximately equal
+** to the size of the original database for the rollback journal.
+** Hence, temporary disk space that is approximately 2x the size of the
+** original database is required. Every page of the database is written
+** approximately 3 times: Once for step (2) and twice for step (3).
+** Two writes per page are required in step (3) because the original
+** database content must be written into the rollback journal prior to
+** overwriting the database with the vacuumed content.
+**
+** Only 1x temporary space and only 1x writes would be required if
+** the copy of step (3) were replaced by deleting the original database
+** and renaming the transient database as the original. But that will
+** not work if other processes are attached to the original database.
+** And a power loss in between deleting the original and renaming the
+** transient would cause the database file to appear to be deleted
+** following reboot.
+*/
+void sqlite3Vacuum(Parse *pParse, Token *pNm, Expr *pInto){
+ Vdbe *v = sqlite3GetVdbe(pParse);
+ int iDb = 0;
+ if( v==0 ) goto build_vacuum_end;
+ if( pParse->nErr ) goto build_vacuum_end;
+ if( pNm ){
+#ifndef SQLITE_BUG_COMPATIBLE_20160819
+ /* Default behavior: Report an error if the argument to VACUUM is
+ ** not recognized */
+ iDb = sqlite3TwoPartName(pParse, pNm, pNm, &pNm);
+ if( iDb<0 ) goto build_vacuum_end;
+#else
+ /* When SQLITE_BUG_COMPATIBLE_20160819 is defined, unrecognized arguments
+ ** to VACUUM are silently ignored. This is a back-out of a bug fix that
+ ** occurred on 2016-08-19 (https://www.sqlite.org/src/info/083f9e6270).
+ ** The buggy behavior is required for binary compatibility with some
+ ** legacy applications. */
+ iDb = sqlite3FindDb(pParse->db, pNm);
+ if( iDb<0 ) iDb = 0;
+#endif
+ }
+ if( iDb!=1 ){
+ int iIntoReg = 0;
+ if( pInto && sqlite3ResolveSelfReference(pParse,0,0,pInto,0)==0 ){
+ iIntoReg = ++pParse->nMem;
+ sqlite3ExprCode(pParse, pInto, iIntoReg);
+ }
+ sqlite3VdbeAddOp2(v, OP_Vacuum, iDb, iIntoReg);
+ sqlite3VdbeUsesBtree(v, iDb);
+ }
+build_vacuum_end:
+ sqlite3ExprDelete(pParse->db, pInto);
+ return;
+}
+
+/*
+** This routine implements the OP_Vacuum opcode of the VDBE.
+*/
+SQLITE_NOINLINE int sqlite3RunVacuum(
+ char **pzErrMsg, /* Write error message here */
+ sqlite3 *db, /* Database connection */
+ int iDb, /* Which attached DB to vacuum */
+ sqlite3_value *pOut /* Write results here, if not NULL. VACUUM INTO */
+){
+ int rc = SQLITE_OK; /* Return code from service routines */
+ Btree *pMain; /* The database being vacuumed */
+ Btree *pTemp; /* The temporary database we vacuum into */
+ u32 saved_mDbFlags; /* Saved value of db->mDbFlags */
+ u64 saved_flags; /* Saved value of db->flags */
+ i64 saved_nChange; /* Saved value of db->nChange */
+ i64 saved_nTotalChange; /* Saved value of db->nTotalChange */
+ u32 saved_openFlags; /* Saved value of db->openFlags */
+ u8 saved_mTrace; /* Saved trace settings */
+ 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 */
+ const char *zDbMain; /* Schema name of database to vacuum */
+ const char *zOut; /* Name of output file */
+ u32 pgflags = PAGER_SYNCHRONOUS_OFF; /* sync flags for output db */
+
+ if( !db->autoCommit ){
+ sqlite3SetString(pzErrMsg, db, "cannot VACUUM from within a transaction");
+ return SQLITE_ERROR; /* IMP: R-12218-18073 */
+ }
+ if( db->nVdbeActive>1 ){
+ sqlite3SetString(pzErrMsg, db,"cannot VACUUM - SQL statements in progress");
+ return SQLITE_ERROR; /* IMP: R-15610-35227 */
+ }
+ saved_openFlags = db->openFlags;
+ if( pOut ){
+ if( sqlite3_value_type(pOut)!=SQLITE_TEXT ){
+ sqlite3SetString(pzErrMsg, db, "non-text filename");
+ return SQLITE_ERROR;
+ }
+ zOut = (const char*)sqlite3_value_text(pOut);
+ db->openFlags &= ~SQLITE_OPEN_READONLY;
+ db->openFlags |= SQLITE_OPEN_CREATE|SQLITE_OPEN_READWRITE;
+ }else{
+ zOut = "";
+ }
+
+ /* 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_mDbFlags = db->mDbFlags;
+ saved_nChange = db->nChange;
+ saved_nTotalChange = db->nTotalChange;
+ saved_mTrace = db->mTrace;
+ db->flags |= SQLITE_WriteSchema | SQLITE_IgnoreChecks;
+ db->mDbFlags |= DBFLAG_PreferBuiltin | DBFLAG_Vacuum;
+ db->flags &= ~(u64)(SQLITE_ForeignKeys | SQLITE_ReverseOrder
+ | SQLITE_Defensive | SQLITE_CountRows);
+ db->mTrace = 0;
+
+ zDbMain = db->aDb[iDb].zDbSName;
+ pMain = db->aDb[iDb].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 optimization 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;
+ rc = execSqlF(db, pzErrMsg, "ATTACH %Q AS vacuum_db", zOut);
+ db->openFlags = saved_openFlags;
+ if( rc!=SQLITE_OK ) goto end_of_vacuum;
+ assert( (db->nDb-1)==nDb );
+ pDb = &db->aDb[nDb];
+ assert( strcmp(pDb->zDbSName,"vacuum_db")==0 );
+ pTemp = pDb->pBt;
+ if( pOut ){
+ sqlite3_file *id = sqlite3PagerFile(sqlite3BtreePager(pTemp));
+ i64 sz = 0;
+ if( id->pMethods!=0 && (sqlite3OsFileSize(id, &sz)!=SQLITE_OK || sz>0) ){
+ rc = SQLITE_ERROR;
+ sqlite3SetString(pzErrMsg, db, "output file already exists");
+ goto end_of_vacuum;
+ }
+ db->mDbFlags |= DBFLAG_VacuumInto;
+
+ /* For a VACUUM INTO, the pager-flags are set to the same values as
+ ** they are for the database being vacuumed, except that PAGER_CACHESPILL
+ ** is always set. */
+ pgflags = db->aDb[iDb].safety_level | (db->flags & PAGER_FLAGS_MASK);
+ }
+ nRes = sqlite3BtreeGetRequestedReserve(pMain);
+
+ sqlite3BtreeSetCacheSize(pTemp, db->aDb[iDb].pSchema->cache_size);
+ sqlite3BtreeSetSpillSize(pTemp, sqlite3BtreeSetSpillSize(pMain,0));
+ sqlite3BtreeSetPagerFlags(pTemp, pgflags|PAGER_CACHESPILL);
+
+ /* Begin a transaction and take an exclusive lock on the main database
+ ** file. This is done before the sqlite3BtreeGetPageSize(pMain) call below,
+ ** to ensure that we do not try to change the page-size on a WAL database.
+ */
+ rc = execSql(db, pzErrMsg, "BEGIN");
+ if( rc!=SQLITE_OK ) goto end_of_vacuum;
+ rc = sqlite3BtreeBeginTrans(pMain, pOut==0 ? 2 : 0, 0);
+ if( rc!=SQLITE_OK ) goto end_of_vacuum;
+
+ /* Do not attempt to change the page size for a WAL database */
+ if( sqlite3PagerGetJournalMode(sqlite3BtreePager(pMain))
+ ==PAGER_JOURNALMODE_WAL
+ && pOut==0
+ ){
+ db->nextPagesize = 0;
+ }
+
+ if( sqlite3BtreeSetPageSize(pTemp, sqlite3BtreeGetPageSize(pMain), nRes, 0)
+ || (!isMemDb && sqlite3BtreeSetPageSize(pTemp, db->nextPagesize, nRes, 0))
+ || NEVER(db->mallocFailed)
+ ){
+ rc = SQLITE_NOMEM_BKPT;
+ goto end_of_vacuum;
+ }
+
+#ifndef SQLITE_OMIT_AUTOVACUUM
+ sqlite3BtreeSetAutoVacuum(pTemp, db->nextAutovac>=0 ? db->nextAutovac :
+ sqlite3BtreeGetAutoVacuum(pMain));
+#endif
+
+ /* Query the schema of the main database. Create a mirror schema
+ ** in the temporary database.
+ */
+ db->init.iDb = nDb; /* force new CREATE statements into vacuum_db */
+ rc = execSqlF(db, pzErrMsg,
+ "SELECT sql FROM \"%w\".sqlite_schema"
+ " WHERE type='table'AND name<>'sqlite_sequence'"
+ " AND coalesce(rootpage,1)>0",
+ zDbMain
+ );
+ if( rc!=SQLITE_OK ) goto end_of_vacuum;
+ rc = execSqlF(db, pzErrMsg,
+ "SELECT sql FROM \"%w\".sqlite_schema"
+ " WHERE type='index'",
+ zDbMain
+ );
+ if( rc!=SQLITE_OK ) goto end_of_vacuum;
+ db->init.iDb = 0;
+
+ /* 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 = execSqlF(db, pzErrMsg,
+ "SELECT'INSERT INTO vacuum_db.'||quote(name)"
+ "||' SELECT*FROM\"%w\".'||quote(name)"
+ "FROM vacuum_db.sqlite_schema "
+ "WHERE type='table'AND coalesce(rootpage,1)>0",
+ zDbMain
+ );
+ assert( (db->mDbFlags & DBFLAG_Vacuum)!=0 );
+ db->mDbFlags &= ~DBFLAG_Vacuum;
+ 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 schema table.
+ */
+ rc = execSqlF(db, pzErrMsg,
+ "INSERT INTO vacuum_db.sqlite_schema"
+ " SELECT*FROM \"%w\".sqlite_schema"
+ " WHERE type IN('view','trigger')"
+ " OR(type='table'AND rootpage=0)",
+ zDbMain
+ );
+ 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 */
+ BTREE_APPLICATION_ID, 0, /* Preserve the application id */
+ };
+
+ assert( SQLITE_TXN_WRITE==sqlite3BtreeTxnState(pTemp) );
+ assert( pOut!=0 || SQLITE_TXN_WRITE==sqlite3BtreeTxnState(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;
+ }
+
+ if( pOut==0 ){
+ 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
+ if( pOut==0 ){
+ sqlite3BtreeSetAutoVacuum(pMain, sqlite3BtreeGetAutoVacuum(pTemp));
+ }
+#endif
+ }
+
+ assert( rc==SQLITE_OK );
+ if( pOut==0 ){
+ nRes = sqlite3BtreeGetRequestedReserve(pTemp);
+ rc = sqlite3BtreeSetPageSize(pMain, sqlite3BtreeGetPageSize(pTemp), nRes,1);
+ }
+
+end_of_vacuum:
+ /* Restore the original value of db->flags */
+ db->init.iDb = 0;
+ db->mDbFlags = saved_mDbFlags;
+ db->flags = saved_flags;
+ db->nChange = saved_nChange;
+ db->nTotalChange = saved_nTotalChange;
+ db->mTrace = saved_mTrace;
+ sqlite3BtreeSetPageSize(pMain, -1, 0, 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. */
+ sqlite3ResetAllSchemasOfConnection(db);
+
+ return rc;
+}
+
+#endif /* SQLITE_OMIT_VACUUM && SQLITE_OMIT_ATTACH */