SQLite

  Parse *pParse,         /* The parser context */
  SrcList *pTabList,     /* The table from which we should delete things */
  Expr *pWhere           /* The WHERE clause.  May be null */
){
  Vdbe *v;               /* The virtual database engine */
  Table *pTab;           /* The table from which records will be deleted */
  const char *zDb;       /* Name of database holding pTab */

  int i;                 /* Loop counter */
  WhereInfo *pWInfo;     /* Information about the WHERE clause */
  Index *pIdx;           /* For looping over indices of the table */
  int iTabCur;           /* Cursor number for the table */
  int iDataCur;          /* VDBE cursor for the canonical data source */
  int iIdxCur;           /* Cursor number of the first index */
  int nIdx;              /* Number of indices */
  sqlite3 *db;           /* Main database structure */
  AuthContext sContext;  /* Authorization context */
  NameContext sNC;       /* Name context to resolve expressions in */
  int iDb;               /* Database number */
  int memCnt = -1;       /* Memory cell used for change counting */
  int rcauth;            /* Value returned by authorization callback */
  int okOnePass;         /* True for one-pass algorithm without the FIFO */
  int aiCurOnePass[2];   /* The write cursors opened by WHERE_ONEPASS */
  u8 *aToOpen = 0;       /* Open cursor iTabCur+j if aToOpen[j] is true */
  Index *pPk;            /* The PRIMARY KEY index on the table */
  int iPk;               /* First of nPk registerss holding PRIMARY KEY value */
  i16 nPk = 1;           /* Number of components of the PRIMARY KEY */
  int iKey;              /* Memory cell holding row key of to be deleted */
  i16 nKey;              /* Number of memory cells of row key */
  int iEphCur = 0;       /* Ephemeral table holding all primary key values */
  int iRowSet = 0;       /* Register for rowset of rows to delete */
  int addrBypass = 0;    /* Address of jump over the delete logic */
  int addrLoop = 0;      /* Top of the delete loop */
  int addrDelete = 0;    /* Jump directly to the delete logic */
  int addrEphOpen = 0;   /* Instruction to open the Ephermeral table */
 
#ifndef SQLITE_OMIT_TRIGGER
  int isView;                  /* True if attempting to delete from a view */
  Trigger *pTrigger;           /* List of table triggers, if required */
#endif

  memset(&sContext, 0, sizeof(sContext));
  db = pParse->db;

    }
    for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
      assert( pIdx->pSchema==pTab->pSchema );
      sqlite3VdbeAddOp2(v, OP_Clear, pIdx->tnum, iDb);
    }
  }else
#endif /* SQLITE_OMIT_TRUNCATE_OPTIMIZATION */
  {
    if( HasRowid(pTab) ){

      /* For a rowid table, initialize the RowSet to an empty set */
      pPk = 0;
      nPk = 1;
      iRowSet = ++pParse->nMem;
      sqlite3VdbeAddOp2(v, OP_Null, 0, iRowSet);
    }else{
      /* For a WITHOUT ROWID table, create an ephermeral table used to


      ** hold all primary keys for rows to be deleted. */
      pPk = sqlite3PrimaryKeyIndex(pTab);
      assert( pPk!=0 );
      nPk = pPk->nKeyCol;
      iPk = pParse->nMem+1;
      pParse->nMem += nPk;

      iEphCur = pParse->nTab++;

      addrEphOpen = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, iEphCur, nPk);
      sqlite3VdbeSetP4KeyInfo(pParse, pPk);
    }
  
    /* Construct a query to find the rowid or primary key for every row
    ** to be deleted, based on the WHERE clause.
    */
    pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, 0, 0, 
                               WHERE_ONEPASS_DESIRED, iTabCur+1);
    if( pWInfo==0 ) goto delete_from_cleanup;
    okOnePass = sqlite3WhereOkOnePass(pWInfo, aiCurOnePass);


  
    /* Keep track of the number of rows to be deleted */
    if( db->flags & SQLITE_CountRows ){
      sqlite3VdbeAddOp2(v, OP_AddImm, memCnt, 1);
    }
  
    /* Extract the rowid or primary key for the current row */
    if( pPk ){
      for(i=0; i<nPk; i++){
        sqlite3ExprCodeGetColumnOfTable(v, pTab, iTabCur,
                                        pPk->aiColumn[i], iPk+i);
      }
      iKey = iPk;
      nKey = nPk;
    }else{
      iKey = pParse->nMem + 1;
      iKey = sqlite3ExprCodeGetColumn(pParse, pTab, -1, iTabCur, iKey, 0);
      if( iKey>pParse->nMem ) pParse->nMem = iKey;
    }
  
    if( okOnePass ){
      /* For ONEPASS, no need to store the rowid/primary-key.  There is only
      ** one, so just keep it in its register(s) and fall through to the
      ** delete code.
      */
      nKey = nPk; /* OP_Found will use an unpacked key */
      aToOpen = sqlite3DbMallocRaw(db, nIdx+2);
      if( aToOpen==0 ) goto delete_from_cleanup;
      memset(aToOpen, 1, nIdx+1);
      aToOpen[nIdx+1] = 0;
      if( aiCurOnePass[0]>=0 ) aToOpen[aiCurOnePass[0]-iTabCur] = 0;
      if( aiCurOnePass[1]>=0 ) aToOpen[aiCurOnePass[1]-iTabCur] = 0;
      if( addrEphOpen ) sqlite3VdbeChangeToNoop(v, addrEphOpen);
      addrDelete = sqlite3VdbeAddOp0(v, OP_Goto); /* Jump to DELETE logic */
    }else if( pPk ){
      /* Construct a composite key for the row to be deleted and remember it */
      iKey = ++pParse->nMem;
      nKey = 0;   /* Zero tells OP_Found to use a composite key */
      sqlite3VdbeAddOp4(v, OP_MakeRecord, iPk, nPk, iKey,
                        sqlite3IndexAffinityStr(v, pPk), P4_TRANSIENT);
      sqlite3VdbeAddOp2(v, OP_IdxInsert, iEphCur, iKey);
    }else{





      /* Get the rowid of the row to be deleted and remember it in the RowSet */




      nKey = 1;  /* OP_Seek always uses a single rowid */



      sqlite3VdbeAddOp2(v, OP_RowSetAdd, iRowSet, iKey);
    }
  




    /* End of the WHERE loop */











































    sqlite3WhereEnd(pWInfo);
    if( okOnePass ){
      /* Bypass the delete logic below if the WHERE loop found zero rows */
      addrBypass = sqlite3VdbeAddOp0(v, OP_Goto);
      sqlite3VdbeJumpHere(v, addrDelete);
    }
  





    /* Unless this is a view, open cursors for the table we are 
    ** deleting from and all its indices. If this is a view, then the
    ** only effect this statement has is to fire the INSTEAD OF 
    ** triggers.
    */
    if( !isView ){
      sqlite3OpenTableAndIndices(pParse, pTab, OP_OpenWrite, iTabCur, aToOpen,
                                 &iDataCur, &iIdxCur);
      assert( pPk || iDataCur==iTabCur );
      assert( pPk || iIdxCur==iDataCur+1 );
    }
  
    /* Set up a loop over the rowids/primary-keys that were found in the
    ** where-clause loop above.
    */
    if( okOnePass ){
      /* Just one row.  Hence the top-of-loop is a no-op */
      assert( nKey==nPk ); /* OP_Found will use an unpacked key */
    }else if( pPk ){
      addrLoop = sqlite3VdbeAddOp1(v, OP_Rewind, iEphCur);
      sqlite3VdbeAddOp2(v, OP_RowKey, iEphCur, iKey);
      assert( nKey==0 );  /* OP_Found will use a composite key */
    }else{
      addrLoop = sqlite3VdbeAddOp3(v, OP_RowSetRead, iRowSet, 0, iKey);
      assert( nKey==1 );
    }  
  
    /* Delete the row */
#ifndef SQLITE_OMIT_VIRTUALTABLE
    if( IsVirtual(pTab) ){
      const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
      sqlite3VtabMakeWritable(pParse, pTab);
      sqlite3VdbeAddOp4(v, OP_VUpdate, 0, 1, iKey, pVTab, P4_VTAB);
      sqlite3VdbeChangeP5(v, OE_Abort);
      sqlite3MayAbort(pParse);
    }else
#endif
    {
      int count = (pParse->nested==0);    /* True to count changes */
      sqlite3GenerateRowDelete(pParse, pTab, pTrigger, iDataCur, iIdxCur,
                               iKey, nKey, count, OE_Default, okOnePass);
    }
  
    /* End of the loop over all rowids/primary-keys. */
    if( okOnePass ){
      sqlite3VdbeJumpHere(v, addrBypass);
    }else if( pPk ){
      sqlite3VdbeAddOp2(v, OP_Next, iEphCur, addrLoop+1);
      sqlite3VdbeJumpHere(v, addrLoop);
    }else{
      sqlite3VdbeAddOp2(v, OP_Goto, 0, addrLoop);
      sqlite3VdbeJumpHere(v, addrLoop);
    }     

  
    /* Close the cursors open on the table and its indexes. */
    if( !isView && !IsVirtual(pTab) ){
      if( !pPk ) sqlite3VdbeAddOp1(v, OP_Close, iDataCur);
      for(i=0, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
        sqlite3VdbeAddOp1(v, OP_Close, iIdxCur + i);
      }
    }
  } /* End non-truncate path */

  /* Update the sqlite_sequence table by storing the content of the
  ** maximum rowid counter values recorded while inserting into
  ** autoincrement tables.
  */
  if( pParse->nested==0 && pParse->pTriggerTab==0 ){
    sqlite3AutoincrementEnd(pParse);