SQLite

    *pUnqual = pName2;
    iDb = sqlite3FindDb(db, pName1);
    if( iDb<0 ){
      sqlite3ErrorMsg(pParse, "unknown database %T", pName1);
      return -1;
    }
  }else{
    assert( db->init.iDb==0 || db->init.busy || (db->flags & SQLITE_Vacuum)!=0);
    iDb = db->init.iDb;
    *pUnqual = pName1;
  }
  return iDb;
}

/*

    sqlite3DbFree(db, zStmt);
    sqlite3ChangeCookie(pParse, iDb);

#ifndef SQLITE_OMIT_AUTOINCREMENT
    /* Check to see if we need to create an sqlite_sequence table for
    ** keeping track of autoincrement keys.
    */
    if( (p->tabFlags & TF_Autoincrement)!=0 ){
      Db *pDb = &db->aDb[iDb];
      assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
      if( pDb->pSchema->pSeqTab==0 ){
        sqlite3NestedParse(pParse,
          "CREATE TABLE %Q.sqlite_sequence(name,seq)",
          pDb->zDbSName
        );

  return 0;
}

#ifndef SQLITE_OMIT_AUTOINCREMENT
/*
** Locate or create an AutoincInfo structure associated with table pTab
** which is in database iDb.  Return the register number for the register
** that holds the maximum rowid.  Return zero if pTab is not an AUTOINCREMENT
** table.  (Also return zero when doing a VACUUM since we do not want to
** update the AUTOINCREMENT counters during a VACUUM.)
**
** There is at most one AutoincInfo structure per table even if the
** same table is autoincremented multiple times due to inserts within
** triggers.  A new AutoincInfo structure is created if this is the
** first use of table pTab.  On 2nd and subsequent uses, the original
** AutoincInfo structure is used.
**

*/
static int autoIncBegin(
  Parse *pParse,      /* Parsing context */
  int iDb,            /* Index of the database holding pTab */
  Table *pTab         /* The table we are writing to */
){
  int memId = 0;      /* Register holding maximum rowid */
  if( (pTab->tabFlags & TF_Autoincrement)!=0
   && (pParse->db->flags & SQLITE_Vacuum)==0
  ){
    Parse *pToplevel = sqlite3ParseToplevel(pParse);
    AutoincInfo *pInfo;

    pInfo = pToplevel->pAinc;
    while( pInfo && pInfo->pTab!=pTab ){ pInfo = pInfo->pNext; }
    if( pInfo==0 ){
      pInfo = sqlite3DbMallocRawNN(pParse->db, sizeof(*pInfo));

//
cmd ::= DROP INDEX ifexists(E) fullname(X).   {sqlite3DropIndex(pParse, X, E);}

///////////////////////////// The VACUUM command /////////////////////////////
//
%ifndef SQLITE_OMIT_VACUUM
%ifndef SQLITE_OMIT_ATTACH
cmd ::= VACUUM.                {sqlite3Vacuum(pParse,0);}
cmd ::= VACUUM nm(X).          {sqlite3Vacuum(pParse,&X);}
%endif  SQLITE_OMIT_ATTACH
%endif  SQLITE_OMIT_VACUUM

///////////////////////////// The PRAGMA command /////////////////////////////
//
%ifndef SQLITE_OMIT_PRAGMA
cmd ::= PRAGMA nm(X) dbnm(Z).                {sqlite3Pragma(pParse,&X,&Z,0,0);}

  }else if( sqlite3_strnicmp(argv[2],"create ",7)==0 ){
    /* Call the parser to process a CREATE TABLE, INDEX or VIEW.
    ** But because db->init.busy is set to 1, no VDBE code is generated
    ** or executed.  All the parser does is build the internal data
    ** structures that describe the table, index, or view.
    */
    int rc;
    u8 saved_iDb = db->init.iDb;
    sqlite3_stmt *pStmt;
    TESTONLY(int rcp);            /* Return code from sqlite3_prepare() */

    assert( db->init.busy );
    db->init.iDb = iDb;
    db->init.newTnum = sqlite3Atoi(argv[1]);
    db->init.orphanTrigger = 0;
    TESTONLY(rcp = ) sqlite3_prepare(db, argv[2], -1, &pStmt, 0);
    rc = db->errCode;
    assert( (rc&0xFF)==(rcp&0xFF) );
    db->init.iDb = saved_iDb;
    assert( saved_iDb==0 || (db->flags & SQLITE_Vacuum)!=0 );
    if( SQLITE_OK!=rc ){
      if( db->init.orphanTrigger ){
        assert( iDb==1 );
      }else{
        pData->rc = rc;
        if( rc==SQLITE_NOMEM ){
          sqlite3OomFault(db);

#define LOCATE_VIEW    0x01
#define LOCATE_NOERR   0x02
Table *sqlite3LocateTable(Parse*,u32 flags,const char*, const char*);
Table *sqlite3LocateTableItem(Parse*,u32 flags,struct SrcList_item *);
Index *sqlite3FindIndex(sqlite3*,const char*, const char*);
void sqlite3UnlinkAndDeleteTable(sqlite3*,int,const char*);
void sqlite3UnlinkAndDeleteIndex(sqlite3*,int,const char*);
void sqlite3Vacuum(Parse*,Token*);
int sqlite3RunVacuum(char**, sqlite3*, int);
char *sqlite3NameFromToken(sqlite3*, Token*);
int sqlite3ExprCompare(Expr*, Expr*, int);
int sqlite3ExprListCompare(ExprList*, ExprList*, int);
int sqlite3ExprImpliesExpr(Expr*, Expr*, int);
void sqlite3ExprAnalyzeAggregates(NameContext*, Expr*);
void sqlite3ExprAnalyzeAggList(NameContext*,ExprList*);
int sqlite3ExprCoveredByIndex(Expr*, int iCur, Index *pIdx);

** 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 );
    if( zSubSql ){
      assert( zSubSql[0]!='S' );
      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:
**

** 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){
  Vdbe *v = sqlite3GetVdbe(pParse);
  int iDb = pNm ? sqlite3TwoPartName(pParse, pNm, pNm, &pNm) : 0;
  if( v && (iDb>=2 || iDb==0) ){
    sqlite3VdbeAddOp1(v, OP_Vacuum, iDb);
    sqlite3VdbeUsesBtree(v, iDb);
  }
  return;
}

/*
** This routine implements the OP_Vacuum opcode of the VDBE.
*/
int sqlite3RunVacuum(char **pzErrMsg, sqlite3 *db, int iDb){
  int rc = SQLITE_OK;     /* Return code from service routines */
  Btree *pMain;           /* The database being vacuumed */
  Btree *pTemp;           /* The temporary database we vacuum into */

  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 */
  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 */

  if( !db->autoCommit ){
    sqlite3SetString(pzErrMsg, db, "cannot VACUUM from within a transaction");
    return SQLITE_ERROR;
  }
  if( db->nVdbeActive>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_mTrace = db->mTrace;
  db->flags |= (SQLITE_WriteSchema | SQLITE_IgnoreChecks
                 | SQLITE_PreferBuiltin | SQLITE_Vacuum);
  db->flags &= ~(SQLITE_ForeignKeys | SQLITE_ReverseOrder | 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 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;





  rc = execSql(db, pzErrMsg, "ATTACH''AS vacuum_db");
  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;

  /* 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 = sqlite3BtreeGetOptimalReserve(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

  sqlite3BtreeSetCacheSize(pTemp, db->aDb[iDb].pSchema->cache_size);
  sqlite3BtreeSetSpillSize(pTemp, sqlite3BtreeSetSpillSize(pMain,0));
  sqlite3BtreeSetPagerFlags(pTemp, PAGER_SYNCHRONOUS_OFF);


  /* 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, 2);
  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 ){

  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_master"
      " 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_master"
      " WHERE type='index' AND length(sql)>10",
      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_master "

      "WHERE type='table'AND coalesce(rootpage,1)>0",
      zDbMain
  );
  assert( (db->flags & SQLITE_Vacuum)!=0 );
  db->flags &= ~SQLITE_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 SQLITE_MASTER table.
  */
  rc = execSqlF(db, pzErrMsg,
      "INSERT INTO vacuum_db.sqlite_master"

      " SELECT*FROM \"%w\".sqlite_master"
      " 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

  }

  assert( rc==SQLITE_OK );
  rc = sqlite3BtreeSetPageSize(pMain, sqlite3BtreeGetPageSize(pTemp), nRes,1);

end_of_vacuum:
  /* Restore the original value of db->flags */
  db->init.iDb = 0;
  db->flags = saved_flags;
  db->nChange = saved_nChange;
  db->nTotalChange = saved_nTotalChange;
  db->mTrace = saved_mTrace;
  sqlite3BtreeSetPageSize(pMain, -1, -1, 1);

  /* Currently there is an SQL level transaction open on the vacuum

  sqlite3VdbeChangeEncoding(pOut, encoding);
  if( rc ) goto abort_due_to_error;
  break;
};
#endif /* SQLITE_OMIT_PRAGMA */

#if !defined(SQLITE_OMIT_VACUUM) && !defined(SQLITE_OMIT_ATTACH)
/* Opcode: Vacuum P1 * * * *
**
** Vacuum the entire database P1.  P1 is 0 for "main", and 2 or more
** for an attached database.  The "temp" database may not be vacuumed.

*/
case OP_Vacuum: {
  assert( p->readOnly==0 );
  rc = sqlite3RunVacuum(&p->zErrMsg, db, pOp->p1);
  if( rc ) goto abort_due_to_error;
  break;
}
#endif

#if !defined(SQLITE_OMIT_AUTOVACUUM)
/* Opcode: IncrVacuum P1 P2 * * *

  ATTACH 'test.db2' AS aux;
  PRAGMA aux.page_size = 1024;
  CREATE TABLE aux.t3 AS SELECT * FROM t1;
  DELETE FROM t3;
} {}
set original_size [file size test.db2]

# Vacuuming the main database does not affect aux
do_execsql_test e_vacuum-2.1.3 { VACUUM } {}




do_test e_vacuum-2.1.6 { expr {[file size test.db2]==$::original_size} } 1

# EVIDENCE-OF: R-17495-17419 The VACUUM command may change the ROWIDs of
# entries in any tables that do not have an explicit INTEGER PRIMARY
# KEY.
#
#   Tests e_vacuum-3.1.1 - 3.1.2 demonstrate that rowids can change when

# 2016-08-19
#
# 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 implements a test for VACUUM on attached databases.
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl

# If the VACUUM statement is disabled in the current build, skip all
# the tests in this file.
#
ifcapable !vacuum {
  finish_test
  return
}

forcedelete test2.db test3.db
do_execsql_test vacuum5-1.1 {
  CREATE TABLE main.t1(a,b);
  WITH RECURSIVE c(x) AS (VALUES(1) UNION ALL SELECT x+1 FROM c WHERE x<1000)
    INSERT INTO t1(a,b) SELECT x, randomblob(1000) FROM c;
  CREATE TEMP TABLE ttemp(x,y);
  INSERT INTO ttemp SELECT * FROM t1;
  ATTACH 'test2.db' AS x2;
  ATTACH 'test3.db' AS x3;
  CREATE TABLE x2.t2(c,d);
  INSERT INTO t2 SELECT * FROM t1;
  CREATE TABLE x3.t3(e,f);
  INSERT INTO t3 SELECT * FROM t1;
  DELETE FROM t1 WHERE (rowid%3)!=0;
  DELETE FROM t2 WHERE (rowid%4)!=0;
  DELETE FROM t3 WHERE (rowid%5)!=0;
  PRAGMA main.integrity_check;
  PRAGMA x2.integrity_check;
  PRAGMA x3.integrity_check;
} {ok ok ok}
set size1 [file size test.db]
set size2 [file size test2.db]
set size3 [file size test3.db]

do_execsql_test vacuum5-1.2.1 {
  VACUUM main;
} {}
do_test vacuum5-1.2.2 {
  expr {[file size test.db]<$size1}
} {1}
do_test vacuum5-1.2.3 {
  file size test2.db
} $size2
do_test vacuum5-1.2.4 {
  file size test3.db
} $size3
set size1 [file size test.db]
do_execsql_test vacuum-1.2.5 {
  DELETE FROM t1;
  PRAGMA main.integrity_check;
} {ok}

do_execsql_test vacuum5-1.3.1 {
  VACUUM x2;
} {}
do_test vacuum5-1.3.2 {
  file size test.db
} $size1
do_test vacuum5-1.3.3 {
  expr {[file size test2.db]<$size2}
} 1
do_test vacuum5-1.3.4 {
  file size test3.db
} $size3
set size2 [file size test2.db]
do_execsql_test vacuum-1.3.5 {
  DELETE FROM t2;
  PRAGMA x2.integrity_check;
} {ok}

do_execsql_test vacuum5-1.4.1 {
  VACUUM x3;
} {}
do_test vacuum5-1.3.2 {
  file size test.db
} $size1
do_test vacuum5-1.3.3 {
  file size test2.db
} $size2
do_test vacuum5-1.3.4 {
  expr {[file size test3.db]<$size3}
} 1

# VACUUM is a no-op on the TEMP table
#
set sizeTemp [db one {PRAGMA temp.page_count}]
do_execsql_test vacuum5-1.4.1 {
  VACUUM temp;
} {}
do_execsql_test vacuum5-1.4.2 {
  PRAGMA temp.page_count;
} $sizeTemp

do_catchsql_test vacuum5-2.0 {
  VACUUM olaf;
} {1 {unknown database olaf}}