SQLite

    int regRowid;                   /* Actual register containing rowids */

    /* Collect rowids of every row to be deleted.
    */
    sqlite3VdbeAddOp2(v, OP_Null, 0, iRowSet);
    pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere,0,WHERE_DUPLICATES_OK);
    if( pWInfo==0 ) goto delete_from_cleanup;
    regRowid = sqlite3ExprCodeGetColumn(pParse, pTab, -1, iCur, iRowid, 0);
    sqlite3VdbeAddOp2(v, OP_RowSetAdd, iRowSet, regRowid);
    if( db->flags & SQLITE_CountRows ){
      sqlite3VdbeAddOp2(v, OP_AddImm, memCnt, 1);
    }
    sqlite3WhereEnd(pWInfo);

    /* Delete every item whose key was written to the list during the

    if( !pColl ){
      pColl = sqlite3ExprCollSeq(pParse, pRight);
    }
  }
  return pColl;
}

/*
** Generate the operands for a comparison operation.  Before
** generating the code for each operand, set the EP_AnyAff
** flag on the expression so that it will be able to used a
** cached column value that has previously undergone an
** affinity change.
*/
static void codeCompareOperands(
  Parse *pParse,    /* Parsing and code generating context */
  Expr *pLeft,      /* The left operand */
  int *pRegLeft,    /* Register where left operand is stored */
  int *pFreeLeft,   /* Free this register when done */
  Expr *pRight,     /* The right operand */
  int *pRegRight,   /* Register where right operand is stored */
  int *pFreeRight   /* Write temp register for right operand there */
){
  while( pLeft->op==TK_UPLUS ) pLeft = pLeft->pLeft;
  pLeft->flags |= EP_AnyAff;
  *pRegLeft = sqlite3ExprCodeTemp(pParse, pLeft, pFreeLeft);
  while( pRight->op==TK_UPLUS ) pRight = pRight->pLeft;
  pRight->flags |= EP_AnyAff;
  *pRegRight = sqlite3ExprCodeTemp(pParse, pRight, pFreeRight);
}

/*
** Generate code for a comparison operator.
*/
static int codeCompare(
  Parse *pParse,    /* The parsing (and code generating) context */
  Expr *pLeft,      /* The left operand */
  Expr *pRight,     /* The right operand */

  int minLru;
  int idxLru;
  struct yColCache *p;

  assert( iReg>0 );  /* Register numbers are always positive */
  assert( iCol>=-1 && iCol<32768 );  /* Finite column numbers */







  /* First replace any existing entry */
  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
    if( p->iReg && p->iTable==iTab && p->iColumn==iCol ){
      cacheEntryClear(pParse, p);
      p->iLevel = pParse->iCacheLevel;
      p->iReg = iReg;
      p->affChange = 0;
      p->lru = pParse->iCacheCnt++;
      return;
    }
  }

  /* Find an empty slot and replace it */
  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
    if( p->iReg==0 ){
      p->iLevel = pParse->iCacheLevel;
      p->iTable = iTab;
      p->iColumn = iCol;
      p->iReg = iReg;
      p->affChange = 0;
      p->tempReg = 0;
      p->lru = pParse->iCacheCnt++;
      return;
    }
  }

  /* Replace the last recently used */

  }
  if( ALWAYS(idxLru>=0) ){
    p = &pParse->aColCache[idxLru];
    p->iLevel = pParse->iCacheLevel;
    p->iTable = iTab;
    p->iColumn = iCol;
    p->iReg = iReg;
    p->affChange = 0;
    p->tempReg = 0;
    p->lru = pParse->iCacheCnt++;
    return;
  }
}

/*

** used if allowAffChng is true.
*/
int sqlite3ExprCodeGetColumn(
  Parse *pParse,   /* Parsing and code generating context */
  Table *pTab,     /* Description of the table we are reading from */
  int iColumn,     /* Index of the table column */
  int iTable,      /* The cursor pointing to the table */
  int iReg,        /* Store results here */
  int allowAffChng /* True if prior affinity changes are OK */
){
  Vdbe *v = pParse->pVdbe;
  int i;
  struct yColCache *p;

  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
    if( p->iReg>0 && p->iTable==iTable && p->iColumn==iColumn
           && (!p->affChange || allowAffChng) ){
      p->lru = pParse->iCacheCnt++;
      sqlite3ExprCachePinRegister(pParse, p->iReg);
      return p->iReg;
    }
  }  
  assert( v!=0 );
  if( iColumn<0 ){

void sqlite3ExprCacheAffinityChange(Parse *pParse, int iStart, int iCount){
  int iEnd = iStart + iCount - 1;
  int i;
  struct yColCache *p;
  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
    int r = p->iReg;
    if( r>=iStart && r<=iEnd ){

      p->affChange = 1;
    }
  }
}

/*
** Generate code to move content from registers iFrom...iFrom+nReg-1
** over to iTo..iTo+nReg-1. Keep the column cache up-to-date.

    }
    case TK_COLUMN: {
      if( pExpr->iTable<0 ){
        /* This only happens when coding check constraints */
        assert( pParse->ckBase>0 );
        inReg = pExpr->iColumn + pParse->ckBase;
      }else{
        testcase( (pExpr->flags & EP_AnyAff)!=0 );
        inReg = sqlite3ExprCodeGetColumn(pParse, pExpr->pTab,
                                 pExpr->iColumn, pExpr->iTable, target,
                                 pExpr->flags & EP_AnyAff);
      }
      break;
    }
    case TK_INTEGER: {
      codeInteger(v, pExpr, 0, target);
      break;
    }

      assert( TK_NE==OP_Ne );
      testcase( op==TK_LT );
      testcase( op==TK_LE );
      testcase( op==TK_GT );
      testcase( op==TK_GE );
      testcase( op==TK_EQ );
      testcase( op==TK_NE );
      codeCompareOperands(pParse, pExpr->pLeft, &r1, &regFree1,
                                  pExpr->pRight, &r2, &regFree2);
      codeCompare(pParse, pExpr->pLeft, pExpr->pRight, op,
                  r1, r2, inReg, SQLITE_STOREP2);
      testcase( regFree1==0 );
      testcase( regFree2==0 );
      break;
    }
    case TK_IS:
    case TK_ISNOT: {
      testcase( op==TK_IS );
      testcase( op==TK_ISNOT );
      codeCompareOperands(pParse, pExpr->pLeft, &r1, &regFree1,
                                  pExpr->pRight, &r2, &regFree2);
      op = (op==TK_IS) ? TK_EQ : TK_NE;
      codeCompare(pParse, pExpr->pLeft, pExpr->pRight, op,
                  r1, r2, inReg, SQLITE_STOREP2 | SQLITE_NULLEQ);
      testcase( regFree1==0 );
      testcase( regFree2==0 );
      break;
    }

    ** Z is stored in pExpr->pList->a[1].pExpr.
    */
    case TK_BETWEEN: {
      Expr *pLeft = pExpr->pLeft;
      struct ExprList_item *pLItem = pExpr->x.pList->a;
      Expr *pRight = pLItem->pExpr;

      codeCompareOperands(pParse, pLeft, &r1, &regFree1,
                                  pRight, &r2, &regFree2);
      testcase( regFree1==0 );
      testcase( regFree2==0 );
      r3 = sqlite3GetTempReg(pParse);
      r4 = sqlite3GetTempReg(pParse);
      codeCompare(pParse, pLeft, pRight, OP_Ge,
                  r1, r2, r3, SQLITE_STOREP2);
      pLItem++;

      testcase( op==TK_LT );
      testcase( op==TK_LE );
      testcase( op==TK_GT );
      testcase( op==TK_GE );
      testcase( op==TK_EQ );
      testcase( op==TK_NE );
      testcase( jumpIfNull==0 );
      codeCompareOperands(pParse, pExpr->pLeft, &r1, &regFree1,
                                  pExpr->pRight, &r2, &regFree2);
      codeCompare(pParse, pExpr->pLeft, pExpr->pRight, op,
                  r1, r2, dest, jumpIfNull);
      testcase( regFree1==0 );
      testcase( regFree2==0 );
      break;
    }
    case TK_IS:
    case TK_ISNOT: {
      testcase( op==TK_IS );
      testcase( op==TK_ISNOT );
      codeCompareOperands(pParse, pExpr->pLeft, &r1, &regFree1,
                                  pExpr->pRight, &r2, &regFree2);
      op = (op==TK_IS) ? TK_EQ : TK_NE;
      codeCompare(pParse, pExpr->pLeft, pExpr->pRight, op,
                  r1, r2, dest, SQLITE_NULLEQ);
      testcase( regFree1==0 );
      testcase( regFree2==0 );
      break;
    }

      testcase( op==TK_LT );
      testcase( op==TK_LE );
      testcase( op==TK_GT );
      testcase( op==TK_GE );
      testcase( op==TK_EQ );
      testcase( op==TK_NE );
      testcase( jumpIfNull==0 );
      codeCompareOperands(pParse, pExpr->pLeft, &r1, &regFree1,
                                  pExpr->pRight, &r2, &regFree2);
      codeCompare(pParse, pExpr->pLeft, pExpr->pRight, op,
                  r1, r2, dest, jumpIfNull);
      testcase( regFree1==0 );
      testcase( regFree2==0 );
      break;
    }
    case TK_IS:
    case TK_ISNOT: {
      testcase( pExpr->op==TK_IS );
      testcase( pExpr->op==TK_ISNOT );
      codeCompareOperands(pParse, pExpr->pLeft, &r1, &regFree1,
                                  pExpr->pRight, &r2, &regFree2);
      op = (pExpr->op==TK_IS) ? TK_NE : TK_EQ;
      codeCompare(pParse, pExpr->pLeft, pExpr->pRight, op,
                  r1, r2, dest, SQLITE_NULLEQ);
      testcase( regFree1==0 );
      testcase( regFree2==0 );
      break;
    }

        for(i=0; i<sAggInfo.nColumn; i++){
          struct AggInfo_col *pCol = &sAggInfo.aCol[i];
          if( pCol->iSorterColumn>=j ){
            int r1 = j + regBase;
            int r2;

            r2 = sqlite3ExprCodeGetColumn(pParse, 
                               pCol->pTab, pCol->iColumn, pCol->iTable, r1, 0);
            if( r1!=r2 ){
              sqlite3VdbeAddOp2(v, OP_SCopy, r2, r1);
            }
            j++;
          }
        }
        regRecord = sqlite3GetTempReg(pParse);

/*
** Bits of the sqlite3.flags field that are used by the
** sqlite3_test_control(SQLITE_TESTCTRL_OPTIMIZATIONS,...) interface.
** These must be the low-order bits of the flags field.
*/
#define SQLITE_QueryFlattener 0x01        /* Disable query flattening */
#define SQLITE_IndexSort      0x02        /* Disable indexes for sorting */
#define SQLITE_IndexSearch    0x04        /* Disable indexes for searching */
#define SQLITE_IndexCover     0x08        /* Disable index covering table */
#define SQLITE_RegisterReuse  0x10        /* Disable register reuse */
#define SQLITE_OptMask        0x1f        /* Mask of all disablable opts */

/*
** Possible values for the sqlite.magic field.
** The numbers are obtained at random and have no special meaning, other
** than being distinct from one another.
*/

#define EP_Resolved   0x0004  /* IDs have been resolved to COLUMNs */
#define EP_Error      0x0008  /* Expression contains one or more errors */
#define EP_Distinct   0x0010  /* Aggregate function with DISTINCT keyword */
#define EP_VarSelect  0x0020  /* pSelect is correlated, not constant */
#define EP_DblQuoted  0x0040  /* token.z was originally in "..." */
#define EP_InfixFunc  0x0080  /* True for an infix function: LIKE, GLOB, etc */
#define EP_ExpCollate 0x0100  /* Collating sequence specified explicitly */
#define EP_AnyAff     0x0200  /* Can take a cached column of any affinity */
#define EP_FixedDest  0x0400  /* Result needed in a specific register */
#define EP_IntValue   0x0800  /* Integer value contained in u.iValue */
#define EP_xIsSelect  0x1000  /* x.pSelect is valid (otherwise x.pList is) */

#define EP_Reduced    0x2000  /* Expr struct is EXPR_REDUCEDSIZE bytes only */
#define EP_TokenOnly  0x4000  /* Expr struct is EXPR_TOKENONLYSIZE bytes only */
#define EP_Static     0x8000  /* Held in memory not obtained from malloc() */

/*
** The following are the meanings of bits in the Expr.flags2 field.
*/
#define EP2_MallocedToken  0x0001  /* Need to sqlite3DbFree() Expr.zToken */
#define EP2_Irreducible    0x0002  /* Cannot EXPRDUP_REDUCE this Expr */

  int iCacheLevel;     /* ColCache valid when aColCache[].iLevel<=iCacheLevel */
  int iCacheCnt;       /* Counter used to generate aColCache[].lru values */
  u8 nColCache;        /* Number of entries in the column cache */
  u8 iColCache;        /* Next entry of the cache to replace */
  struct yColCache {
    int iTable;           /* Table cursor number */
    int iColumn;          /* Table column number */
    u8 affChange;         /* True if this register has had an affinity change */
    u8 tempReg;           /* iReg is a temp register that needs to be freed */
    int iLevel;           /* Nesting level */
    int iReg;             /* Reg with value of this column. 0 means none. */
    int lru;              /* Least recently used entry has the smallest value */
  } aColCache[SQLITE_N_COLCACHE];  /* One for each column cache entry */
  u32 writeMask;       /* Start a write transaction on these databases */
  u32 cookieMask;      /* Bitmask of schema verified databases */

#if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) && !defined(SQLITE_OMIT_SUBQUERY)
Expr *sqlite3LimitWhere(Parse *, SrcList *, Expr *, ExprList *, Expr *, Expr *, char *);
#endif
void sqlite3DeleteFrom(Parse*, SrcList*, Expr*);
void sqlite3Update(Parse*, SrcList*, ExprList*, Expr*, int);
WhereInfo *sqlite3WhereBegin(Parse*, SrcList*, Expr*, ExprList**, u16);
void sqlite3WhereEnd(WhereInfo*);
int sqlite3ExprCodeGetColumn(Parse*, Table*, int, int, int, int);
void sqlite3ExprCodeMove(Parse*, int, int, int);
void sqlite3ExprCodeCopy(Parse*, int, int, int);
void sqlite3ExprCacheStore(Parse*, int, int, int);
void sqlite3ExprCachePush(Parse*);
void sqlite3ExprCachePop(Parse*, int);
void sqlite3ExprCacheRemove(Parse*, int);
void sqlite3ExprCacheClear(Parse*);

                        WHERE_OMIT_OPEN | WHERE_OMIT_CLOSE |
                        WHERE_FORCE_TABLE | WHERE_ONETABLE_ONLY);
        if( pSubWInfo ){
          if( (wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
            int iSet = ((ii==pOrWc->nTerm-1)?-1:ii);
            int r;
            r = sqlite3ExprCodeGetColumn(pParse, pTabItem->pTab, -1, iCur, 
                                         regRowid, 0);
            sqlite3VdbeAddOp4Int(v, OP_RowSetTest, regRowset,
                                 sqlite3VdbeCurrentAddr(v)+2, r, iSet);
          }
          sqlite3VdbeAddOp2(v, OP_Gosub, regReturn, iLoopBody);

          /* The pSubWInfo->untestedTerms flag means that this OR term
          ** contained one or more AND term from a notReady table.  The