SQLite

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

///////////////////////////// The VACUUM command /////////////////////////////
//
%ifndef SQLITE_OMIT_VACUUM
%ifndef SQLITE_OMIT_ATTACH
%type vinto {Token}
cmd ::= VACUUM vinto(Y).                {sqlite3Vacuum(pParse,0,&Y);}
cmd ::= VACUUM nm(X) vinto(Y).          {sqlite3Vacuum(pParse,&X,&Y);}
vinto(A) ::= INTO nm(X).                {A = X;}
vinto(A) ::= .                          {A.z = 0;}
%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);}

#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*,Token*);
int sqlite3RunVacuum(char**, sqlite3*, int, const char*);
char *sqlite3NameFromToken(sqlite3*, Token*);
int sqlite3ExprCompare(Parse*,Expr*, Expr*, int);
int sqlite3ExprCompareSkip(Expr*, Expr*, int);
int sqlite3ExprListCompare(ExprList*, ExprList*, int);
int sqlite3ExprImpliesExpr(Parse*,Expr*, Expr*, int);
int sqlite3ExprImpliesNonNullRow(Expr*,int);
void sqlite3ExprAnalyzeAggregates(NameContext*, Expr*);

** 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, Token *pInto){
  Vdbe *v = sqlite3GetVdbe(pParse);
  int iDb = 0;
  assert( pInto!=0 );
  if( v==0 ) return;
  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 ) return;
#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 ){
    sqlite3VdbeAddOp1(v, OP_Vacuum, iDb);
    sqlite3VdbeUsesBtree(v, iDb);
    if( pInto->z ){
      char *zName = sqlite3NameFromToken(pParse->db, pInto);
      sqlite3VdbeChangeP4(v, -1, zName, P4_DYNAMIC);
    }
  }
  return;
}

/*
** This routine implements the OP_Vacuum opcode of the VDBE.
*/
int sqlite3RunVacuum(char **pzErrMsg, sqlite3 *db, int iDb, const char *zOut){
  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 */
  int saved_nChange;      /* Saved value of db->nChange */
  int saved_nTotalChange; /* Saved value of db->nTotalChange */

  ** 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 ? zOut : "");
  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

  /* 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, zOut==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 ){
    db->nextPagesize = 0;
  }

       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( 1==sqlite3BtreeIsInTrans(pTemp) );
    assert( zOut!=0 || 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;
    }

    if( zOut==0 ){
      rc = sqlite3BtreeCopyFile(pMain, pTemp);
    }else{
      rc = sqlite3BtreeCommit(pMain);
    }
    if( rc!=SQLITE_OK ) goto end_of_vacuum;
    rc = sqlite3BtreeCommit(pTemp);
    if( rc!=SQLITE_OK ) goto end_of_vacuum;
#ifndef SQLITE_OMIT_AUTOVACUUM
    if( zOut==0 ){
      sqlite3BtreeSetAutoVacuum(pMain, sqlite3BtreeGetAutoVacuum(pTemp));
    }
#endif
  }

  assert( rc==SQLITE_OK );
  if( zOut==0 ){
    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;

  if( pDb ){
    sqlite3BtreeClose(pDb->pBt);
    pDb->pBt = 0;
    pDb->pSchema = 0;
  }

  if( zOut==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 */

  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 * * P4 *
**
** 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.
**
** If P4 is not a NULL pointer, then it is a UTF8 string which is the
** name of a file into which to write the result of the vacuum.  When
** P4 is NULL, the result of vacuum overwrites the original database.
*/
case OP_Vacuum: {
  assert( p->readOnly==0 );
  rc = sqlite3RunVacuum(&p->zErrMsg, db, pOp->p1, pOp->p4.z);
  if( rc ) goto abort_due_to_error;
  break;
}
#endif

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