SQLite

        if( sqlite3FixSelect(pFix, pExpr->x.pSelect) ) return 1;
        break;
      }
      case EX_List: {
        if( sqlite3FixExprList(pFix, pExpr->x.pList) ) return 1;
        break;
      }

      case EX_Right: {
        if( sqlite3FixExpr(pFix, pExpr->x.pRight) ) return 1;
        break;
      }
    }
    pExpr = pExpr->pLeft;
  }
  return 0;
}
int sqlite3FixExprList(
  DbFixer *pFix,     /* Context of the fixation */

      pColl = sqlite3GetCollSeq(pParse, ENC(db), 0, p->u.zToken);
      break;
    }
    if( p->flags & EP_Collate ){
      if( p->pLeft && (p->pLeft->flags & EP_Collate)!=0 ){
        p = p->pLeft;
      }else{
        Expr *pNext = 0;
        /* p->flags holds EP_Collate and p->pLeft->flags does not.  And
        ** p->x.pSelect cannot.  So if p->x.pLeft exists, it must hold at
        ** least one EP_Collate. Thus the following two ALWAYS. */
        if( p->eX==EX_List ){
          int i;
          for(i=0; ALWAYS(i<p->x.pList->nExpr); i++){
            if( ExprHasProperty(p->x.pList->a[i].pExpr, EP_Collate) ){
              pNext = p->x.pList->a[i].pExpr;
              break;
            }
          }
        }else if( p->eX==EX_Right ){
          pNext = p->x.pRight;
        }
        p = pNext;
      }
    }else{
      break;
    }
  }

static char comparisonAffinity(Expr *pExpr){
  char aff;
  assert( pExpr->op==TK_EQ || pExpr->op==TK_IN || pExpr->op==TK_LT ||
          pExpr->op==TK_GT || pExpr->op==TK_GE || pExpr->op==TK_LE ||
          pExpr->op==TK_NE || pExpr->op==TK_IS || pExpr->op==TK_ISNOT );
  assert( pExpr->pLeft );
  aff = sqlite3ExprAffinity(pExpr->pLeft);
  if( pExpr->eX==EX_Right ){
    aff = sqlite3CompareAffinity(pExpr->x.pRight, aff);
  }else if( pExpr->eX==EX_Select ){
    aff = sqlite3CompareAffinity(pExpr->x.pSelect->pEList->a[0].pExpr, aff);
  }else if( aff==0 ){
    aff = SQLITE_AFF_BLOB;
  }
  return aff;
}

** If the left hand expression has a collating sequence type, then it is
** used. Otherwise the collation sequence for the right hand expression
** is used, or the default (BINARY) if neither expression has a collating
** type.
**
** Argument pRight (but not pLeft) may be a null pointer. In this case,
** it is not considered.
**
** The second form (sqlite3BinaryExprCollSeq()) uses the Expr.pLeft
** and Expr.x.pRight pointer from the second argument instead of separate
** pointers.
*/
CollSeq *sqlite3ComparisonCollSeq(
  Parse *pParse, 
  Expr *pLeft, 
  Expr *pRight
){
  CollSeq *pColl;
  assert( pLeft );
  if( pLeft->flags & EP_Collate ){
    pColl = sqlite3ExprCollSeq(pParse, pLeft);
  }else if( pRight && (pRight->flags & EP_Collate)!=0 ){
    pColl = sqlite3ExprCollSeq(pParse, pRight);
  }else{
    pColl = sqlite3ExprCollSeq(pParse, pLeft);
    if( !pColl ){
      pColl = sqlite3ExprCollSeq(pParse, pRight);
    }
  }
  return pColl;
}
CollSeq *sqlite3ComparisonExprCollSeq(Parse *pParse, Expr *pExpr){
  if( pExpr->eX==EX_Right ){
    return sqlite3ComparisonCollSeq(pParse, pExpr->pLeft, pExpr->x.pRight);
  }else{
    return sqlite3ComparisonCollSeq(pParse, pExpr->pLeft, 0);
  }
}

/*
** 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 opcode,       /* The comparison opcode */
  int in1, int in2, /* Register holding operands */
  int dest,         /* Jump here if true.  */
  int jumpIfNull    /* If true, jump if either operand is NULL */
){
  int p5;
  int addr;
  CollSeq *p4;

  p4 = sqlite3ComparisonCollSeq(pParse, pLeft, pRight);
  p5 = binaryCompareP5(pLeft, pRight, jumpIfNull);
  addr = sqlite3VdbeAddOp4(pParse->pVdbe, opcode, in2, dest, in1,
                           (void*)p4, P4_COLLSEQ);
  sqlite3VdbeChangeP5(pParse->pVdbe, (u8)p5);
  return addr;
}

  Expr *pExpr,          /* The comparison operation */
  int dest,             /* Write results into this register */
  u8 op,                /* Comparison operator */
  u8 p5                 /* SQLITE_NULLEQ or zero */
){
  Vdbe *v = pParse->pVdbe;
  Expr *pLeft = pExpr->pLeft;
  Expr *pRight = pExpr->x.pRight;
  int nLeft = sqlite3ExprVectorSize(pLeft);
  int i;
  int regLeft = 0;
  int regRight = 0;
  u8 opx = op;
  int addrDone = sqlite3VdbeMakeLabel(v);

**
** Also propagate EP_Propagate flags up from Expr.x.pList to Expr.flags,
** if appropriate.
*/
static void exprSetHeight(Expr *p){
  int nHeight = 0;
  heightOfExpr(p->pLeft, &nHeight);
  switch( p->eX ){
    case EX_Select: {
      heightOfSelect(p->x.pSelect, &nHeight);
      break;
    }
    case EX_List: {
      heightOfExprList(p->x.pList, &nHeight);
      p->flags |= EP_Propagate & sqlite3ExprListFlags(p->x.pList);
      break;
    }
    case EX_Right: {
      heightOfExpr(p->x.pRight, &nHeight);
      break;
    }
  }
  p->nHeight = nHeight + 1;
}

/*
** Set the Expr.nHeight variable using the exprSetHeight() function. If
** the height is greater than the maximum allowed expression depth,

){
  if( pRoot==0 ){
    assert( db->mallocFailed );
    sqlite3ExprDelete(db, pLeft);
    sqlite3ExprDelete(db, pRight);
  }else{
    if( pRight ){
      assert( pRoot->eX==EX_None );
      pRoot->x.pRight = pRight;
      pRoot->eX = EX_Right;
      pRoot->flags |= EP_Propagate & pRight->flags;
    }
    if( pLeft ){
      pRoot->pLeft = pLeft;
      pRoot->flags |= EP_Propagate & pLeft->flags;
    }
    exprSetHeight(pRoot);

  /* Sanity check: Assert that the IntValue is non-negative if it exists */
  assert( !ExprHasProperty(p, EP_IntValue) || p->u.iValue>=0 );
  assert( p->eX!=EX_Select || p->x.pSelect!=0 );
  assert( p->eX!=EX_List || p->x.pList!=0 );
#ifdef SQLITE_DEBUG
  if( ExprHasProperty(p, EP_Leaf) && !ExprHasProperty(p, EP_TokenOnly) ){
    assert( p->pLeft==0 );

    assert( p->eX==EX_None );
  }
  if( !ExprHasProperty(p, EP_TokenOnly) ){
    assert( p->op!=TK_FUNCTION || p->pLeft==0 );

  }
  if( !ExprHasProperty(p, (EP_TokenOnly|EP_Reduced)) ){
    assert( p->pWin==0 || p->pLeft==0 );
    assert( p->pWin==0 || p->pTab==0 );
    assert( p->pWin==0 || p->op==TK_FUNCTION );
    assert( p->pTab==0 || p->eX==EX_None );
  }
#endif
  if( !ExprHasProperty(p, (EP_TokenOnly|EP_Leaf)) ){


    if( p->pLeft && p->op!=TK_SELECT_COLUMN ) sqlite3ExprDeleteNN(db, p->pLeft);



    switch( p->eX ){
      case EX_Select: {
        sqlite3SelectDelete(db, p->x.pSelect);
        break;
      }
      case EX_List: {
        sqlite3ExprListDelete(db, p->x.pList);
        break;
      }
      case EX_Right: {
        sqlite3ExprDelete(db, p->x.pRight);
        break;
      }
    }
    if( !ExprHasProperty(p, EP_Reduced) ){
      sqlite3WindowDelete(db, p->pWin);
    }
  }
  if( ExprHasProperty(p, EP_MemToken) ) sqlite3DbFree(db, p->u.zToken);

  ){
    nSize = EXPR_FULLSIZE;
  }else{
    assert( !ExprHasProperty(p, EP_TokenOnly|EP_Reduced) );
    assert( !ExprHasProperty(p, EP_FromJoin) ); 
    assert( !ExprHasProperty(p, EP_MemToken) );
    assert( !ExprHasProperty(p, EP_NoReduce) );
    if( p->pLeft || p->eX!=EX_None ){
      nSize = EXPR_REDUCEDSIZE | EP_Reduced;
    }else{

      nSize = EXPR_TOKENONLYSIZE | EP_TokenOnly;
    }
  }
  return nSize;
}

/*

** descended from the Expr.x.pList or Expr.x.pSelect variables).
*/
static int dupedExprSize(Expr *p, int flags){
  int nByte = 0;
  if( p ){
    nByte = dupedExprNodeSize(p, flags);
    if( flags&EXPRDUP_REDUCE ){
      nByte += dupedExprSize(p->pLeft, flags);
      if( p->eX==EX_Right ) nByte += dupedExprSize(p->x.pRight, flags);
    }
  }
  return nByte;
}

/*
** This function is similar to sqlite3ExprDup(), except that if pzBuffer 
** is not NULL then *pzBuffer is assumed to point to a buffer large enough 
** to store the copy of expression p, the copies of p->u.zToken
** (if applicable), and the copies of the p->pLeft and p->x.pRight expressions,
** if any. Before returning, *pzBuffer is set to the first byte past the
** portion of the buffer copied into by this function.
*/
static Expr *exprDup(sqlite3 *db, Expr *p, int dupFlags, u8 **pzBuffer){
  Expr *pNew;           /* Value to return */
  u8 *zAlloc;           /* Memory space from which to build Expr object */
  u32 staticFlag;       /* EP_Static if space not obtained from malloc */

          pNew->x.pList = sqlite3ExprListDup(db, p->x.pList, dupFlags);
          if( pNew->x.pList==0 ) pNew->eX = EX_None;
          break;
        }
      }
    }

    /* Fill in pNew->pLeft and pNew->x.pRight. */
    if( ExprHasProperty(pNew, EP_Reduced|EP_TokenOnly) ){
      zAlloc += dupedExprNodeSize(p, dupFlags);
      if( !ExprHasProperty(pNew, EP_TokenOnly|EP_Leaf) ){
        pNew->pLeft = p->pLeft ?
                      exprDup(db, p->pLeft, EXPRDUP_REDUCE, &zAlloc) : 0;
        if( p->eX==EX_Right ){
          pNew->x.pRight = exprDup(db, p->x.pRight, EXPRDUP_REDUCE, &zAlloc);
        }
      }
      if( pzBuffer ){
        *pzBuffer = zAlloc;
      }
    }else{
#ifndef SQLITE_OMIT_WINDOWFUNC
      if( ExprHasProperty(p, EP_Reduced|EP_TokenOnly) ){
        pNew->pWin = 0;
      }else{
        pNew->pWin = sqlite3WindowDup(db, pNew, p->pWin);
      }
#endif /* SQLITE_OMIT_WINDOWFUNC */
      if( !ExprHasProperty(p, EP_TokenOnly|EP_Leaf) ){
        if( pNew->op==TK_SELECT_COLUMN ){
          pNew->pLeft = p->pLeft;
          assert( p->iColumn==0 || p->eX!=EX_Right );
          /* OLD: assert( p->pRight==0  || p->x.pRight==p->pLeft ); */
        }else{
          pNew->pLeft = sqlite3ExprDup(db, p->pLeft, 0);
        }
        if( p->eX==EX_Right ){
          pNew->x.pRight = sqlite3ExprDup(db, p->x.pRight, 0);
        }
      }
    }
  }
  return pNew;
}

/*

    pItem->pExpr = sqlite3ExprDup(db, pOldExpr, flags);
    if( pOldExpr 
     && pOldExpr->op==TK_SELECT_COLUMN
     && (pNewExpr = pItem->pExpr)!=0 
    ){
      assert( pNewExpr->iColumn==0 || i>0 );
      if( pNewExpr->iColumn==0 ){
        assert( pOldExpr->pLeft==pOldExpr->x.pRight );
        pPriorSelectCol = pNewExpr->pLeft = pNewExpr->x.pRight;
      }else{
        assert( i>0 );
        assert( pItem[-1].pExpr!=0 );
        assert( pNewExpr->iColumn==pItem[-1].pExpr->iColumn+1 );
        assert( pPriorSelectCol==pItem[-1].pExpr->pLeft );
        pNewExpr->pLeft = pPriorSelectCol;
      }

  if( !db->mallocFailed && pExpr->op==TK_SELECT && ALWAYS(pList!=0) ){
    Expr *pFirst = pList->a[iFirst].pExpr;
    assert( pFirst!=0 );
    assert( pFirst->op==TK_SELECT_COLUMN );
     
    /* Store the SELECT statement in pRight so it will be deleted when
    ** sqlite3ExprListDelete() is called */
    assert( pFirst->eX==EX_None );
    pFirst->x.pRight = pExpr;
    pFirst->eX = EX_Right;
    pExpr = 0;

    /* Remember the size of the LHS in iTable so that we can check that
    ** the RHS and LHS sizes match during code generation. */
    pFirst->iTable = pColumns->nId;
  }

            }
          }
  
          colUsed = 0;   /* Columns of index used so far */
          for(i=0; i<nExpr; i++){
            Expr *pLhs = sqlite3VectorFieldSubexpr(pX->pLeft, i);
            Expr *pRhs = pEList->a[i].pExpr;
            CollSeq *pReq = sqlite3ComparisonCollSeq(pParse, pLhs, pRhs);
            int j;
  
            assert( pReq!=0 || pRhs->iColumn==XN_ROWID || pParse->nErr );
            for(j=0; j<nExpr; j++){
              if( pIdx->aiColumn[j]!=pRhs->iColumn ) continue;
              assert( pIdx->azColl[j] );
              if( pReq!=0 && sqlite3StrICmp(pReq->zName, pIdx->azColl[j])!=0 ){

          sqlite3DbFree(pParse->db, dest.zAffSdst);
          assert( pKeyInfo!=0 ); /* OOM will cause exit after sqlite3Select() */
          assert( pEList!=0 );
          assert( pEList->nExpr>0 );
          assert( sqlite3KeyInfoIsWriteable(pKeyInfo) );
          for(i=0; i<nVal; i++){
            Expr *p = sqlite3VectorFieldSubexpr(pLeft, i);
            pKeyInfo->aColl[i] = sqlite3ComparisonCollSeq(
                pParse, p, pEList->a[i].pExpr
            );
          }
        }
      }else if( ALWAYS(pExpr->x.pList!=0) ){
        /* Case 2:     expr IN (exprlist)
        **

    case TK_NE:
    case TK_EQ: {
      Expr *pLeft = pExpr->pLeft;
      if( sqlite3ExprIsVector(pLeft) ){
        codeVectorCompare(pParse, pExpr, target, op, p5);
      }else{
        r1 = sqlite3ExprCodeTemp(pParse, pLeft, &regFree1);
        assert( pExpr->eX==EX_Right );
        r2 = sqlite3ExprCodeTemp(pParse, pExpr->x.pRight, &regFree2);
        codeCompare(pParse, pLeft, pExpr->x.pRight, op,
            r1, r2, inReg, SQLITE_STOREP2 | p5);
        assert(TK_LT==OP_Lt); testcase(op==OP_Lt); VdbeCoverageIf(v,op==OP_Lt);
        assert(TK_LE==OP_Le); testcase(op==OP_Le); VdbeCoverageIf(v,op==OP_Le);
        assert(TK_GT==OP_Gt); testcase(op==OP_Gt); VdbeCoverageIf(v,op==OP_Gt);
        assert(TK_GE==OP_Ge); testcase(op==OP_Ge); VdbeCoverageIf(v,op==OP_Ge);
        assert(TK_EQ==OP_Eq); testcase(op==OP_Eq); VdbeCoverageIf(v,op==OP_Eq);
        assert(TK_NE==OP_Ne); testcase(op==OP_Ne); VdbeCoverageIf(v,op==OP_Ne);

      assert( TK_BITAND==OP_BitAnd );      testcase( op==TK_BITAND );
      assert( TK_BITOR==OP_BitOr );        testcase( op==TK_BITOR );
      assert( TK_SLASH==OP_Divide );       testcase( op==TK_SLASH );
      assert( TK_LSHIFT==OP_ShiftLeft );   testcase( op==TK_LSHIFT );
      assert( TK_RSHIFT==OP_ShiftRight );  testcase( op==TK_RSHIFT );
      assert( TK_CONCAT==OP_Concat );      testcase( op==TK_CONCAT );
      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
      assert( pExpr->eX==EX_Right );
      r2 = sqlite3ExprCodeTemp(pParse, pExpr->x.pRight, &regFree2);
      sqlite3VdbeAddOp3(v, op, r2, r1, target);
      testcase( regFree1==0 );
      testcase( regFree2==0 );
      break;
    }
    case TK_UMINUS: {
      Expr *pLeft = pExpr->pLeft;

      break;
    }
    case TK_TRUTH: {
      int isTrue;    /* IS TRUE or IS NOT TRUE */
      int bNormal;   /* IS TRUE or IS FALSE */
      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
      testcase( regFree1==0 );
      assert( pExpr->eX==EX_Right );
      isTrue = sqlite3ExprTruthValue(pExpr->x.pRight);
      bNormal = pExpr->op2==TK_IS;
      testcase( isTrue && bNormal);
      testcase( !isTrue && bNormal);
      sqlite3VdbeAddOp4Int(v, OP_IsTrue, r1, inReg, !isTrue, isTrue ^ bNormal);
      break;
    }
    case TK_ISNULL:

        ** So make sure that the regFree1 register is not reused for other
        ** purposes and possibly overwritten.  */
        regFree1 = 0;
      }
      for(i=0; i<nExpr-1; i=i+2){
        if( pX ){
          assert( pTest!=0 );
          opCompare.x.pRight = aListelem[i].pExpr;
          opCompare.eX = EX_Right;
        }else{
          pTest = aListelem[i].pExpr;
        }
        nextCase = sqlite3VdbeMakeLabel(v);
        testcase( pTest->op==TK_COLUMN );
        sqlite3ExprIfFalse(pParse, pTest, nextCase, SQLITE_JUMPIFNULL);
        testcase( aListelem[i+1].pExpr->op==TK_COLUMN );

  memset(&compRight, 0, sizeof(Expr));
  memset(&exprAnd, 0, sizeof(Expr));

  assert( pExpr->eX==EX_List );
  exprX = *pExpr->pLeft;
  exprAnd.op = TK_AND;
  exprAnd.pLeft = &compLeft;
  exprAnd.x.pRight = &compRight;
  exprAnd.eX = EX_Right;
  compLeft.op = TK_GE;
  compLeft.pLeft = &exprX;
  compLeft.x.pRight = pExpr->x.pList->a[0].pExpr;
  compLeft.eX = EX_Right;
  compRight.op = TK_LE;
  compRight.pLeft = &exprX;
  compRight.x.pRight = pExpr->x.pList->a[1].pExpr;
  compRight.eX = EX_Right;
  exprToRegister(&exprX, exprCodeVector(pParse, &exprX, &regFree1));
  if( xJump ){
    xJump(pParse, &exprAnd, dest, jumpIfNull);
  }else{
    /* Mark the expression is being from the ON or USING clause of a join
    ** so that the sqlite3ExprCodeTarget() routine will not attempt to move
    ** it into the Parse.pConstExpr list.  We should use a new bit for this,

  if( NEVER(pExpr==0) ) return;  /* No way this can happen */
  op = pExpr->op;
  switch( op ){
    case TK_AND: {
      int d2 = sqlite3VdbeMakeLabel(v);
      testcase( jumpIfNull==0 );
      sqlite3ExprIfFalse(pParse, pExpr->pLeft, d2,jumpIfNull^SQLITE_JUMPIFNULL);
      assert( pExpr->eX==EX_Right );
      sqlite3ExprIfTrue(pParse, pExpr->x.pRight, dest, jumpIfNull);
      sqlite3VdbeResolveLabel(v, d2);
      break;
    }
    case TK_OR: {
      testcase( jumpIfNull==0 );
      sqlite3ExprIfTrue(pParse, pExpr->pLeft, dest, jumpIfNull);
      assert( pExpr->eX==EX_Right );
      sqlite3ExprIfTrue(pParse, pExpr->x.pRight, dest, jumpIfNull);
      break;
    }
    case TK_NOT: {
      testcase( jumpIfNull==0 );
      sqlite3ExprIfFalse(pParse, pExpr->pLeft, dest, jumpIfNull);
      break;
    }
    case TK_TRUTH: {
      int isNot;      /* IS NOT TRUE or IS NOT FALSE */
      int isTrue;     /* IS TRUE or IS NOT TRUE */
      testcase( jumpIfNull==0 );
      isNot = pExpr->op2==TK_ISNOT;
      assert( pExpr->eX==EX_Right );
      isTrue = sqlite3ExprTruthValue(pExpr->x.pRight);
      testcase( isTrue && isNot );
      testcase( !isTrue && isNot );
      if( isTrue ^ isNot ){
        sqlite3ExprIfTrue(pParse, pExpr->pLeft, dest,
                          isNot ? SQLITE_JUMPIFNULL : 0);
      }else{
        sqlite3ExprIfFalse(pParse, pExpr->pLeft, dest,

    case TK_GT:
    case TK_GE:
    case TK_NE:
    case TK_EQ: {
      if( sqlite3ExprIsVector(pExpr->pLeft) ) goto default_expr;
      testcase( jumpIfNull==0 );
      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
      assert( pExpr->eX==EX_Right );
      r2 = sqlite3ExprCodeTemp(pParse, pExpr->x.pRight, &regFree2);
      codeCompare(pParse, pExpr->pLeft, pExpr->x.pRight, op,
                  r1, r2, dest, jumpIfNull);
      assert(TK_LT==OP_Lt); testcase(op==OP_Lt); VdbeCoverageIf(v,op==OP_Lt);
      assert(TK_LE==OP_Le); testcase(op==OP_Le); VdbeCoverageIf(v,op==OP_Le);
      assert(TK_GT==OP_Gt); testcase(op==OP_Gt); VdbeCoverageIf(v,op==OP_Gt);
      assert(TK_GE==OP_Ge); testcase(op==OP_Ge); VdbeCoverageIf(v,op==OP_Ge);
      assert(TK_EQ==OP_Eq); testcase(op==OP_Eq);
      VdbeCoverageIf(v, op==OP_Eq && jumpIfNull==SQLITE_NULLEQ);

  assert( pExpr->op!=TK_GT || op==OP_Le );
  assert( pExpr->op!=TK_GE || op==OP_Lt );

  switch( pExpr->op ){
    case TK_AND: {
      testcase( jumpIfNull==0 );
      sqlite3ExprIfFalse(pParse, pExpr->pLeft, dest, jumpIfNull);
      assert( pExpr->eX==EX_Right );
      sqlite3ExprIfFalse(pParse, pExpr->x.pRight, dest, jumpIfNull);
      break;
    }
    case TK_OR: {
      int d2 = sqlite3VdbeMakeLabel(v);
      testcase( jumpIfNull==0 );
      sqlite3ExprIfTrue(pParse, pExpr->pLeft, d2, jumpIfNull^SQLITE_JUMPIFNULL);
      assert( pExpr->eX==EX_Right );
      sqlite3ExprIfFalse(pParse, pExpr->x.pRight, dest, jumpIfNull);
      sqlite3VdbeResolveLabel(v, d2);
      break;
    }
    case TK_NOT: {
      testcase( jumpIfNull==0 );
      sqlite3ExprIfTrue(pParse, pExpr->pLeft, dest, jumpIfNull);
      break;
    }
    case TK_TRUTH: {
      int isNot;   /* IS NOT TRUE or IS NOT FALSE */
      int isTrue;  /* IS TRUE or IS NOT TRUE */
      testcase( jumpIfNull==0 );
      isNot = pExpr->op2==TK_ISNOT;
      assert( pExpr->eX==EX_Right );
      isTrue = sqlite3ExprTruthValue(pExpr->x.pRight);
      testcase( isTrue && isNot );
      testcase( !isTrue && isNot );
      if( isTrue ^ isNot ){
        /* IS TRUE and IS NOT FALSE */
        sqlite3ExprIfFalse(pParse, pExpr->pLeft, dest,
                           isNot ? 0 : SQLITE_JUMPIFNULL);

    case TK_GT:
    case TK_GE:
    case TK_NE:
    case TK_EQ: {
      if( sqlite3ExprIsVector(pExpr->pLeft) ) goto default_expr;
      testcase( jumpIfNull==0 );
      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
      assert( pExpr->eX==EX_Right );
      r2 = sqlite3ExprCodeTemp(pParse, pExpr->x.pRight, &regFree2);
      codeCompare(pParse, pExpr->pLeft, pExpr->x.pRight, op,
                  r1, r2, dest, jumpIfNull);
      assert(TK_LT==OP_Lt); testcase(op==OP_Lt); VdbeCoverageIf(v,op==OP_Lt);
      assert(TK_LE==OP_Le); testcase(op==OP_Le); VdbeCoverageIf(v,op==OP_Le);
      assert(TK_GT==OP_Gt); testcase(op==OP_Gt); VdbeCoverageIf(v,op==OP_Gt);
      assert(TK_GE==OP_Ge); testcase(op==OP_Ge); VdbeCoverageIf(v,op==OP_Ge);
      assert(TK_EQ==OP_Eq); testcase(op==OP_Eq);
      VdbeCoverageIf(v, op==OP_Eq && jumpIfNull!=SQLITE_NULLEQ);

    }
  }
  if( (pA->flags & EP_Distinct)!=(pB->flags & EP_Distinct) ) return 2;
  if( ALWAYS((combinedFlags & EP_TokenOnly)==0) ){
    if( pA->eX==EX_Select || pA->eX!=pB->eX ) return 2;
    if( (combinedFlags & EP_FixedCol)==0
     && sqlite3ExprCompare(pParse, pA->pLeft, pB->pLeft, iTab) ) return 2;
    if( pA->eX==EX_Right ){
      if( sqlite3ExprCompare(pParse,pA->x.pRight,pB->x.pRight,iTab) ) return 2;
    }
    if( pA->eX==EX_List ){
      if( sqlite3ExprListCompare(pA->x.pList, pB->x.pList, iTab) ) return 2;
    }
    assert( (combinedFlags & EP_Reduced)==0 );
    if( pA->op!=TK_STRING && pA->op!=TK_TRUEFALSE ){
      if( pA->iColumn!=pB->iColumn ) return 2;
      if( pA->iTable!=pB->iTable 

** improvement.  Returning false might cause a performance reduction, but
** it will always give the correct answer and is hence always safe.
*/
int sqlite3ExprImpliesExpr(Parse *pParse, Expr *pE1, Expr *pE2, int iTab){
  if( sqlite3ExprCompare(pParse, pE1, pE2, iTab)==0 ){
    return 1;
  }
  assert( pE2->op!=TK_OR || pE2->eX==EX_Right );
  if( pE2->op==TK_OR
   && (sqlite3ExprImpliesExpr(pParse, pE1, pE2->pLeft, iTab)
             || sqlite3ExprImpliesExpr(pParse, pE1, pE2->x.pRight, iTab) )
  ){
    return 1;
  }
  if( pE2->op==TK_NOTNULL && pE1->op!=TK_ISNULL && pE1->op!=TK_IS ){
    Expr *pX = sqlite3ExprSkipCollate(pE1->pLeft);
    testcase( pX!=pE1->pLeft );
    if( sqlite3ExprCompare(pParse, pX, pE2->pLeft, iTab)==0 ) return 1;

    case TK_GE:
      testcase( pExpr->op==TK_EQ );
      testcase( pExpr->op==TK_NE );
      testcase( pExpr->op==TK_LT );
      testcase( pExpr->op==TK_LE );
      testcase( pExpr->op==TK_GT );
      testcase( pExpr->op==TK_GE );
      assert( pExpr->eX==EX_Right );
      if( (pExpr->pLeft->op==TK_COLUMN && IsVirtual(pExpr->pLeft->pTab))
       || (pExpr->x.pRight->op==TK_COLUMN && IsVirtual(pExpr->x.pRight->pTab))
      ){
       return WRC_Prune;
      }
    default:
      return WRC_Continue;
  }
}

    if( p ){
      /* memset(p, 0, sizeof(Expr)); */
      p->op = (u8)op;
      p->affinity = 0;
      p->eX = EX_None;
      p->flags = EP_Leaf;
      p->iAgg = -1;
      p->pLeft = 0;
      p->pAggInfo = 0;
      p->pTab = 0;
      p->op2 = 0;
      p->iTable = 0;
      p->iColumn = 0;
#ifndef SQLITE_OMIT_WINDOWFUNC
      p->pWin = 0;

expr(A) ::= expr(A) NOT NULL.    {A = sqlite3PExpr(pParse,TK_NOTNULL,A,0);}

%include {
  /* A routine to convert a binary TK_IS or TK_ISNOT expression into a
  ** unary TK_ISNULL or TK_NOTNULL expression. */
  static void binaryToUnaryIfNull(Parse *pParse, Expr *pY, Expr *pA, int op){
    sqlite3 *db = pParse->db;
    if( pA && pY && pY->op==TK_NULL && pA->eX==EX_Right && !IN_RENAME_OBJECT ){
      pA->op = (u8)op;
      sqlite3ExprDelete(db, pA->x.pRight);
      pA->x.pRight = 0;
      pA->eX = EX_None;
    }
  }
}

//    expr1 IS expr2
//    expr1 IS NOT expr2
//

**    pExpr->iTable        Set to the cursor number for the table obtained
**                         from pSrcList.
**    pExpr->pTab          Points to the Table structure of X.Y (even if
**                         X and/or Y are implied.)
**    pExpr->iColumn       Set to the column number within the table.
**    pExpr->op            Set to TK_COLUMN.
**    pExpr->pLeft         Any expression this points to is deleted
**    pExpr->x.pRight      Any expression this points to is deleted.
**
** The zDb variable is the name of the database (the "X").  This value may be
** NULL meaning that name is of the form Y.Z or Z.  Any available database
** can be used.  The zTable variable is the name of the table (the "Y").  This
** value can be NULL if zDb is also NULL.  If zTable is NULL it
** means that the form of the name is Z and that columns from any table
** can be used.

    ){
      pEList = pNC->uNC.pEList;
      assert( pEList!=0 );
      for(j=0; j<pEList->nExpr; j++){
        char *zAs = pEList->a[j].zName;
        if( zAs!=0 && sqlite3StrICmp(zAs, zCol)==0 ){
          Expr *pOrig;
          assert( pExpr->pLeft==0 );
          assert( pExpr->eX==EX_None );
          pOrig = pEList->a[j].pExpr;
          if( (pNC->ncFlags&NC_AllowAgg)==0 && ExprHasProperty(pOrig, EP_Agg) ){
            sqlite3ErrorMsg(pParse, "misuse of aliased aggregate %s", zAs);
            return WRC_Abort;
          }
          if( sqlite3ExprVectorSize(pOrig)!=1 ){

    pMatch->colUsed |= ((Bitmask)1)<<n;
  }

  /* Clean up and return
  */
  sqlite3ExprDelete(db, pExpr->pLeft);
  pExpr->pLeft = 0;
  if( pExpr->eX==EX_Right ){
    sqlite3ExprDelete(db, pExpr->x.pRight);
    pExpr->x.pRight = 0;
    pExpr->eX = EX_None;
  }
  pExpr->op = eNewExprOp;
  ExprSetProperty(pExpr, EP_Leaf);
lookupname_end:
  if( cnt==1 ){
    assert( pNC!=0 );
    if( !ExprHasProperty(pExpr, EP_Alias) ){
      sqlite3AuthRead(pParse, pExpr, pSchema, pNC->pSrcList);

      if( pExpr->op==TK_ID ){
        zDb = 0;
        zTable = 0;
        zColumn = pExpr->u.zToken;
      }else{
        Expr *pLeft = pExpr->pLeft;
        notValid(pParse, pNC, "the \".\" operator", NC_IdxExpr);
        assert( pExpr->eX==EX_Right );
        pRight = pExpr->x.pRight;
        if( pRight->op==TK_ID ){
          zDb = 0;
        }else{
          assert( pRight->op==TK_DOT );
          assert( pRight->eX==EX_Right );
          zDb = pLeft->u.zToken;
          pLeft = pRight->pLeft;
          pRight = pRight->x.pRight;
        }
        zTable = pLeft->u.zToken;
        zColumn = pRight->u.zToken;
        if( IN_RENAME_OBJECT ){
          sqlite3RenameTokenRemap(pParse, (void*)pExpr, (void*)pRight);
        }
        if( IN_RENAME_OBJECT ){

    }
    case TK_IS:
    case TK_ISNOT: {
      Expr *pRight;
      assert( !ExprHasProperty(pExpr, EP_Reduced) );
      /* Handle special cases of "x IS TRUE", "x IS FALSE", "x IS NOT TRUE",
      ** and "x IS NOT FALSE". */
      assert( pExpr->eX==EX_Right );
      if( (pRight = pExpr->x.pRight)->op==TK_ID ){
        int rc = resolveExprStep(pWalker, pRight);
        if( rc==WRC_Abort ) return WRC_Abort;
        if( pRight->op==TK_TRUEFALSE ){
          pExpr->op2 = pExpr->op;
          pExpr->op = TK_TRUTH;
          return WRC_Continue;
        }

      nLeft = sqlite3ExprVectorSize(pExpr->pLeft);
      if( pExpr->op==TK_BETWEEN ){
        nRight = sqlite3ExprVectorSize(pExpr->x.pList->a[0].pExpr);
        if( nRight==nLeft ){
          nRight = sqlite3ExprVectorSize(pExpr->x.pList->a[1].pExpr);
        }
      }else{
        assert( pExpr->eX==EX_Right );
        nRight = sqlite3ExprVectorSize(pExpr->x.pRight);
      }
      if( nLeft!=nRight ){
        testcase( pExpr->op==TK_EQ );
        testcase( pExpr->op==TK_NE );
        testcase( pExpr->op==TK_LT );
        testcase( pExpr->op==TK_LE );
        testcase( pExpr->op==TK_GT );

*/
static void setJoinExpr(Expr *p, int iTable){
  while( p ){
    ExprSetProperty(p, EP_FromJoin);
    assert( !ExprHasProperty(p, EP_TokenOnly|EP_Reduced) );
    ExprSetVVAProperty(p, EP_NoReduce);
    p->iRightJoinTable = (i16)iTable;
    if( p->op==TK_FUNCTION && p->eX==EX_List ){
      int i;
      for(i=0; i<p->x.pList->nExpr; i++){
        setJoinExpr(p->x.pList->a[i].pExpr, iTable);
      }
    }
    setJoinExpr(p->pLeft, iTable);
    p = p->eX==EX_Right ? p->x.pRight : 0;
  } 
}

/* Undo the work of setJoinExpr().  In the expression tree p, convert every
** term that is marked with EP_FromJoin and iRightJoinTable==iTable into
** an ordinary term that omits the EP_FromJoin mark.
**
** This happens when a LEFT JOIN is simplified into an ordinary JOIN.
*/
static void unsetJoinExpr(Expr *p, int iTable){
  while( p ){
    if( ExprHasProperty(p, EP_FromJoin)
     && (iTable<0 || p->iRightJoinTable==iTable) ){
      ExprClearProperty(p, EP_FromJoin);
    }
    if( p->op==TK_FUNCTION && p->eX==EX_List ){
      int i;
      for(i=0; i<p->x.pList->nExpr; i++){
        unsetJoinExpr(p->x.pList->a[i].pExpr, iTable);
      }
    }
    unsetJoinExpr(p->pLeft, iTable);
    p = p->eX==EX_Right ? p->x.pRight : 0;
  } 
}

/*
** This routine processes the join information for a SELECT statement.
** ON and USING clauses are converted into extra terms of the WHERE clause.
** NATURAL joins also create extra WHERE clause terms.

    /* Get an appropriate name for the column
    */
    if( (zName = pEList->a[i].zName)!=0 ){
      /* If the column contains an "AS <name>" phrase, use <name> as the name */
    }else{
      Expr *pColExpr = sqlite3ExprSkipCollate(pEList->a[i].pExpr);
      while( pColExpr->op==TK_DOT ){
        assert( pColExpr->eX==EX_Right );
        pColExpr = pColExpr->x.pRight;
        assert( pColExpr!=0 );
      }
      assert( pColExpr->op!=TK_AGG_COLUMN );
      if( pColExpr->op==TK_COLUMN ){
        /* For columns use the column name name */
        int iCol = pColExpr->iColumn;
        Table *pTab = pColExpr->pTab;

  }
  return sqlite3VdbeCreate(pParse);
}


/*
** Compute the iLimit and iOffset fields of the SELECT based on the
** pLimit expressions.  pLimit->pLeft and pLimit->x,pRight hold the expressions
** that appear in the original SQL statement after the LIMIT and OFFSET
** keywords.  Or NULL if those keywords are omitted. iLimit and iOffset 
** are the integer memory register numbers for counters used to compute 
** the limit and offset.  If there is no limit and/or offset, then 
** iLimit and iOffset are negative.
**
** This routine changes the values of iLimit and iOffset only if
** a limit or offset is defined by pLimit->pLeft and pLimit->x.pRight.  iLimit
** and iOffset should have been preset to appropriate default values (zero)
** prior to calling this routine.
**
** The iOffset register (if it exists) is initialized to the value
** of the OFFSET.  The iLimit register is initialized to LIMIT.  Register
** iOffset+1 is initialized to LIMIT+OFFSET.
**

      }
    }else{
      sqlite3ExprCode(pParse, pLimit->pLeft, iLimit);
      sqlite3VdbeAddOp1(v, OP_MustBeInt, iLimit); VdbeCoverage(v);
      VdbeComment((v, "LIMIT counter"));
      sqlite3VdbeAddOp2(v, OP_IfNot, iLimit, iBreak); VdbeCoverage(v);
    }
    if( pLimit->eX==EX_Right ){
      p->iOffset = iOffset = ++pParse->nMem;
      pParse->nMem++;   /* Allocate an extra register for limit+offset */
      sqlite3ExprCode(pParse, pLimit->x.pRight, iOffset);
      sqlite3VdbeAddOp1(v, OP_MustBeInt, iOffset); VdbeCoverage(v);
      VdbeComment((v, "OFFSET counter"));
      sqlite3VdbeAddOp3(v, OP_OffsetLimit, iLimit, iOffset+1, iOffset);
      VdbeComment((v, "LIMIT+OFFSET"));
    }
  }
}

    if( pExpr->iColumn<0 ){
      pExpr->op = TK_NULL;
    }else{
      Expr *pNew;
      Expr *pCopy = pSubst->pEList->a[pExpr->iColumn].pExpr;
      Expr ifNullRow;
      assert( pSubst->pEList!=0 && pExpr->iColumn<pSubst->pEList->nExpr );
      assert( pExpr->eX!=EX_Right );
      if( sqlite3ExprIsVector(pCopy) ){
        sqlite3VectorErrorMsg(pSubst->pParse, pCopy);
      }else{
        sqlite3 *db = pSubst->pParse->db;
        if( pSubst->isLeftJoin && pCopy->op!=TK_COLUMN ){
          memset(&ifNullRow, 0, sizeof(ifNullRow));
          ifNullRow.op = TK_IF_NULL_ROW;

      }
    }
  }else{
    if( pExpr->op==TK_IF_NULL_ROW && pExpr->iTable==pSubst->iTable ){
      pExpr->iTable = pSubst->iNewTable;
    }
    pExpr->pLeft = substExpr(pSubst, pExpr->pLeft);

    switch( pExpr->eX ){
      case EX_Select: {
        substSelect(pSubst, pExpr->x.pSelect, 1);
        break;
      }
      case EX_List: {
        substExprList(pSubst, pExpr->x.pList);
        break;
      }
      case EX_Right: {
        pExpr->x.pRight = substExpr(pSubst, pExpr->x.pRight);
        break;
      }
    }
  }
  return pExpr;
}
static void substExprList(
  SubstContext *pSubst, /* Description of the substitution */

  assert( pSubSrc );
  /* Prior to version 3.1.2, when LIMIT and OFFSET had to be simple constants,
  ** not arbitrary expressions, we allowed some combining of LIMIT and OFFSET
  ** because they could be computed at compile-time.  But when LIMIT and OFFSET
  ** became arbitrary expressions, we were forced to add restrictions (13)
  ** and (14). */
  if( pSub->pLimit && p->pLimit ) return 0;              /* Restriction (13) */
  if( pSub->pLimit && pSub->pLimit->eX==EX_Right ){
    return 0;                                            /* Restriction (14) */
  }
  if( (p->selFlags & SF_Compound)!=0 && pSub->pLimit ){
    return 0;                                            /* Restriction (15) */
  }
  if( pSubSrc->nSrc==0 ) return 0;                       /* Restriction (7)  */
  if( pSub->selFlags & SF_Distinct ) return 0;           /* Restriction (4)  */
  if( pSub->pLimit && (pSrc->nSrc>1 || isAgg) ){
     return 0;         /* Restrictions (8)(9) */

** found, add it to the pConst structure.
*/
static void findConstInWhere(WhereConst *pConst, Expr *pExpr){
  Expr *pRight, *pLeft;
  if( pExpr==0 ) return;
  if( ExprHasProperty(pExpr, EP_FromJoin) ) return;
  if( pExpr->op==TK_AND ){
    assert( pExpr->eX==EX_Right );
    findConstInWhere(pConst, pExpr->x.pRight);
    findConstInWhere(pConst, pExpr->pLeft);
    return;
  }
  if( pExpr->op!=TK_EQ ) return;
  assert( pExpr->eX==EX_Right );
  pRight = pExpr->x.pRight;
  pLeft = pExpr->pLeft;
  assert( pRight!=0 );
  assert( pLeft!=0 );
  if( pRight->op==TK_COLUMN
   && !ExprHasProperty(pRight, EP_FixedCol)
   && sqlite3ExprIsConstant(pLeft)
   && sqlite3IsBinary(sqlite3ComparisonCollSeq(pConst->pParse,pLeft,pRight))
  ){
    constInsert(pConst, pRight, pLeft);
  }else
  if( pLeft->op==TK_COLUMN
   && !ExprHasProperty(pLeft, EP_FixedCol)
   && sqlite3ExprIsConstant(pRight)
   && sqlite3IsBinary(sqlite3ComparisonCollSeq(pConst->pParse,pLeft,pRight))
  ){
    constInsert(pConst, pLeft, pRight);
  }
}

/*
** This is a Walker expression callback.  pExpr is a candidate expression

  }
#endif

  if( pSubq->pLimit!=0 ){
    return 0; /* restriction (3) */
  }
  while( pWhere->op==TK_AND ){
    assert( pWhere->eX==EX_Right );
    nChng += pushDownWhereTerms(pParse, pSubq, pWhere->x.pRight,
                                iCursor, isLeftJoin);
    pWhere = pWhere->pLeft;
  }
  if( isLeftJoin
   && (ExprHasProperty(pWhere,EP_FromJoin)==0
         || pWhere->iRightJoinTable!=iCursor)
  ){

  **
  ** The first loop just checks to see if there are any "*" operators
  ** that need expanding.
  */
  for(k=0; k<pEList->nExpr; k++){
    pE = pEList->a[k].pExpr;
    if( pE->op==TK_ASTERISK ) break;
    assert( pE->op!=TK_DOT || pE->eX==EX_Right );
    assert( pE->op!=TK_DOT || (pE->pLeft!=0 && pE->pLeft->op==TK_ID) );
    if( pE->op==TK_DOT && pE->x.pRight->op==TK_ASTERISK ) break;
    elistFlags |= pE->flags;
  }
  if( k<pEList->nExpr ){
    /*
    ** If we get here it means the result set contains one or more "*"
    ** operators that need to be expanded.  Loop through each expression
    ** in the result set and expand them one by one.
    */
    struct ExprList_item *a = pEList->a;
    ExprList *pNew = 0;
    int flags = pParse->db->flags;
    int longNames = (flags & SQLITE_FullColNames)!=0
                      && (flags & SQLITE_ShortColNames)==0;

    for(k=0; k<pEList->nExpr; k++){
      pE = a[k].pExpr;
      elistFlags |= pE->flags;
      pRight = pE->eX==EX_Right ? pE->x.pRight : 0;
      assert( pE->op!=TK_DOT || pRight!=0 );
      if( pE->op!=TK_ASTERISK
       && (pE->op!=TK_DOT || pRight->op!=TK_ASTERISK)
      ){
        /* This particular expression does not need to be expanded.
        */
        pNew = sqlite3ExprListAppend(pParse, pNew, a[k].pExpr);

  /* If the EP_TokenOnly flag is set in the Expr.flags mask, then no
  ** space is allocated for the fields below this point. An attempt to
  ** access them will result in a segfault or malfunction.
  *********************************************************************/

  Expr *pLeft;           /* Left subnode */

  union {
    Expr *pRight;        /* Right subnode */
    ExprList *pList;     /* op = IN, EXISTS, SELECT, CASE, FUNCTION, BETWEEN */
    Select *pSelect;     /* EP_xIsSelect and op = IN, EXISTS, SELECT */
  } x;

  /* If the EP_Reduced flag is set in the Expr.flags mask, then no
  ** space is allocated for the fields below this point. An attempt to
  ** access them will result in a segfault or malfunction.

FuncDef *sqlite3VtabOverloadFunction(sqlite3 *,FuncDef*, int nArg, Expr*);
sqlite3_int64 sqlite3StmtCurrentTime(sqlite3_context*);
int sqlite3VdbeParameterIndex(Vdbe*, const char*, int);
int sqlite3TransferBindings(sqlite3_stmt *, sqlite3_stmt *);
void sqlite3ParserReset(Parse*);
int sqlite3Reprepare(Vdbe*);
void sqlite3ExprListCheckLength(Parse*, ExprList*, const char*);
CollSeq *sqlite3ComparisonCollSeq(Parse*,Expr*,Expr*);
CollSeq *sqlite3ComparisonExprCollSeq(Parse*,Expr*);
int sqlite3TempInMemory(const sqlite3*);
const char *sqlite3JournalModename(int);
#ifndef SQLITE_OMIT_WAL
  int sqlite3Checkpoint(sqlite3*, int, int, int*, int*);
  int sqlite3WalDefaultHook(void*,sqlite3*,const char*,int);
#endif
#ifndef SQLITE_OMIT_CTE

    }
#endif
    if( p->pOrderBy ){
      sqlite3TreeViewExprList(pView, p->pOrderBy, (n--)>0, "ORDERBY");
    }
    if( p->pLimit ){
      sqlite3TreeViewItem(pView, "LIMIT", (n--)>0);
      sqlite3TreeViewExpr(pView, p->pLimit->pLeft, p->pLimit->eX==EX_Right);
      if( p->pLimit->eX==EX_Right ){
        sqlite3TreeViewItem(pView, "OFFSET", (n--)>0);
        sqlite3TreeViewExpr(pView, p->pLimit->x.pRight, 0);
        sqlite3TreeViewPop(pView);
      }
      sqlite3TreeViewPop(pView);
    }
    if( p->pPrior ){
      const char *zOp = "UNION";
      switch( p->op ){

    case TK_TRUTH: {
      int x;
      const char *azOp[] = {
         "IS-FALSE", "IS-TRUE", "IS-NOT-FALSE", "IS-NOT-TRUE"
      };
      assert( pExpr->op2==TK_IS || pExpr->op2==TK_ISNOT );
      assert( pExpr->eX==EX_Right );
      assert( pExpr->x.pRight->op==TK_TRUEFALSE );
      x = (pExpr->op2==TK_ISNOT)*2 + sqlite3ExprTruthValue(pExpr->x.pRight);
      zUniOp = azOp[x];
      break;
    }

    case TK_SPAN: {
      sqlite3TreeViewLine(pView, "SPAN %Q", pExpr->u.zToken);
      sqlite3TreeViewExpr(pView, pExpr->pLeft, 0);

      sqlite3TreeViewLine(pView, "RAISE %s(%Q)", zType, pExpr->u.zToken);
      break;
    }
#endif
    case TK_MATCH: {
      sqlite3TreeViewLine(pView, "MATCH {%d:%d}%s",
                          pExpr->iTable, pExpr->iColumn, zFlgs);
      assert( pExpr->eX==EX_Right );
      sqlite3TreeViewExpr(pView, pExpr->x.pRight, 0);
      break;
    }
    case TK_VECTOR: {
      sqlite3TreeViewBareExprList(pView, pExpr->x.pList, "VECTOR");
      break;
    }
    case TK_SELECT_COLUMN: {

      sqlite3TreeViewLine(pView, "op=%d", pExpr->op);
      break;
    }
  }
  if( zBinOp ){
    sqlite3TreeViewLine(pView, "%s%s", zBinOp, zFlgs);
    sqlite3TreeViewExpr(pView, pExpr->pLeft, 1);
    assert( pExpr->eX==EX_Right );
    sqlite3TreeViewExpr(pView, pExpr->x.pRight, 0);
  }else if( zUniOp ){
    sqlite3TreeViewLine(pView, "%s%s", zUniOp, zFlgs);
    sqlite3TreeViewExpr(pView, pExpr->pLeft, 0);
  }
  sqlite3TreeViewPop(pView);
}

      sqlite3_str_appendf(p, "%s", "expr");
      break;
  }

  if( zOp ){
    sqlite3_str_appendf(p, "%s(", zOp);
    displayP4Expr(p, pExpr->pLeft);
    if( pExpr->eX==EX_Right ){
      sqlite3_str_append(p, ",", 1);
      displayP4Expr(p, pExpr->x.pRight);
    }
    sqlite3_str_append(p, ")", 1);
  }
}
#endif /* VDBE_DISPLAY_P4 && defined(SQLITE_ENABLE_CURSOR_HINTS) */

  testcase( ExprHasProperty(pExpr, EP_TokenOnly) );
  testcase( ExprHasProperty(pExpr, EP_Reduced) );
  while(1){
    rc = pWalker->xExprCallback(pWalker, pExpr);
    if( rc ) return rc & WRC_Abort;
    if( !ExprHasProperty(pExpr,(EP_TokenOnly|EP_Leaf)) ){
      if( pExpr->pLeft && walkExpr(pWalker, pExpr->pLeft) ) return WRC_Abort;
      switch( pExpr->eX ){
        case EX_Right: {
          pExpr = pExpr->x.pRight;
          continue;


        }
        case EX_Select: {
          if( sqlite3WalkSelect(pWalker, pExpr->x.pSelect) ) return WRC_Abort;
          break;
        }
        case EX_List: {
          if( sqlite3WalkExprList(pWalker, pExpr->x.pList) ) return WRC_Abort;
          break;

        }
      }
#ifndef SQLITE_OMIT_WINDOWFUNC
      if( !ExprHasProperty(pExpr, EP_Reduced) && pExpr->pWin ){
        Window *pWin = pExpr->pWin;
        if( sqlite3WalkExprList(pWalker, pWin->pPartition) ) return WRC_Abort;
        if( sqlite3WalkExprList(pWalker, pWin->pOrderBy) ) return WRC_Abort;

         && (iColumn!=XN_EXPR
             || sqlite3ExprCompareSkip(pTerm->pExpr->pLeft,
                                       pScan->pIdxExpr,iCur)==0)
         && (pScan->iEquiv<=1 || !ExprHasProperty(pTerm->pExpr, EP_FromJoin))
        ){
          if( (pTerm->eOperator & WO_EQUIV)!=0
           && pScan->nEquiv<ArraySize(pScan->aiCur)
           && ALWAYS(pTerm->pExpr->eX==EX_Right)
           && (pX = sqlite3ExprSkipCollate(pTerm->pExpr->x.pRight))->op
                       ==TK_COLUMN
          ){
            int j;
            for(j=0; j<pScan->nEquiv; j++){
              if( pScan->aiCur[j]==pX->iTable
               && pScan->aiColumn[j]==pX->iColumn ){
                  break;
              }

              CollSeq *pColl;
              Parse *pParse = pWC->pWInfo->pParse;
              pX = pTerm->pExpr;
              if( !sqlite3IndexAffinityOk(pX, pScan->idxaff) ){
                continue;
              }
              assert(pX->pLeft);
              pColl = sqlite3ComparisonExprCollSeq(pParse, pX);

              if( pColl==0 ) pColl = pParse->db->pDfltColl;
              if( sqlite3StrICmp(pColl->zName, pScan->zCollName) ){
                continue;
              }
            }
            if( (pTerm->eOperator & (WO_EQ|WO_IS))!=0
             && ALWAYS(pTerm->pExpr->eX==EX_Right)
             && (pX = pTerm->pExpr->x.pRight)->op==TK_COLUMN
             && pX->iTable==pScan->aiCur[0]
             && pX->iColumn==pScan->aiColumn[0]
            ){
              testcase( pTerm->eOperator & WO_IS );
              continue;
            }
            pScan->pWC = pWC;

      Bitmask cMask = iCol>=BMS ? MASKBIT(BMS-1) : MASKBIT(iCol);
      testcase( iCol==BMS-1 );
      testcase( iCol==BMS );
      if( (idxCols & cMask)==0 ){
        Expr *pX = pTerm->pExpr;
        idxCols |= cMask;
        pIdx->aiColumn[n] = pTerm->u.leftColumn;
        pColl = sqlite3ComparisonExprCollSeq(pParse, pX);
        pIdx->azColl[n] = pColl ? pColl->zName : sqlite3StrBINARY;
        n++;
      }
    }
  }
  assert( (u32)n==pLoop->u.btree.nEq );

      assert( WO_LT==SQLITE_INDEX_CONSTRAINT_LT );
      assert( WO_LE==SQLITE_INDEX_CONSTRAINT_LE );
      assert( WO_GT==SQLITE_INDEX_CONSTRAINT_GT );
      assert( WO_GE==SQLITE_INDEX_CONSTRAINT_GE );
      assert( pTerm->eOperator&(WO_IN|WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE|WO_AUX) );

      if( op & (WO_LT|WO_LE|WO_GT|WO_GE)
       && ALWAYS(pTerm->pExpr->eX==EX_Right)
       && sqlite3ExprIsVector(pTerm->pExpr->x.pRight) 
      ){
        if( i<16 ) mNoOmit |= (1 << i);
        if( op==WO_LT ) pIdxCons[j].op = WO_LE;
        if( op==WO_GT ) pIdxCons[j].op = WO_GE;
      }
    }

  
  sqlite3_value *p1 = 0;          /* Value extracted from pLower */
  sqlite3_value *p2 = 0;          /* Value extracted from pUpper */
  sqlite3_value *pVal = 0;        /* Value extracted from record */

  pColl = sqlite3LocateCollSeq(pParse, p->azColl[nEq]);
  if( pLower ){
    assert( pLower->pExpr->eX==EX_Right );
    rc = sqlite3Stat4ValueFromExpr(pParse, pLower->pExpr->x.pRight, aff, &p1);
    nLower = 0;
  }
  if( pUpper && rc==SQLITE_OK ){
    assert( pUpper->pExpr->eX==EX_Right );
    rc = sqlite3Stat4ValueFromExpr(pParse, pUpper->pExpr->x.pRight, aff, &p2);
    nUpper = p2 ? 0 : p->nSample;
  }

  if( p1 || p2 ){
    int i;
    int nDiff;
    for(i=0; rc==SQLITE_OK && i<p->nSample; i++){

        SWAP(WhereTerm*, pLower, pUpper);
        SWAP(int, nBtm, nTop);
      }

      /* If possible, improve on the iLower estimate using ($P:$L). */
      if( pLower ){
        int n;                    /* Values extracted from pExpr */
        Expr *pExpr;
        assert( pLower->pExpr->eX==EX_Right );
        pExpr = pLower->pExpr->x.pRight;
        rc = sqlite3Stat4ProbeSetValue(pParse, p, &pRec, pExpr, nBtm, nEq, &n);
        if( rc==SQLITE_OK && n ){
          tRowcnt iNew;
          u16 mask = WO_GT|WO_LE;
          if( sqlite3ExprVectorSize(pExpr)>n ) mask = (WO_LE|WO_LT);
          iLwrIdx = whereKeyStats(pParse, p, pRec, 0, a);
          iNew = a[0] + ((pLower->eOperator & mask) ? a[1] : 0);
          if( iNew>iLower ) iLower = iNew;
          nOut--;
          pLower = 0;
        }
      }

      /* If possible, improve on the iUpper estimate using ($P:$U). */
      if( pUpper ){
        int n;                    /* Values extracted from pExpr */
        Expr *pExpr;
        assert( pUpper->pExpr->eX==EX_Right );
        pExpr = pUpper->pExpr->x.pRight;
        rc = sqlite3Stat4ProbeSetValue(pParse, p, &pRec, pExpr, nTop, nEq, &n);
        if( rc==SQLITE_OK && n ){
          tRowcnt iNew;
          u16 mask = WO_GT|WO_LE;
          if( sqlite3ExprVectorSize(pExpr)>n ) mask = (WO_LE|WO_LT);
          iUprIdx = whereKeyStats(pParse, p, pRec, 1, a);
          iNew = a[0] + ((pUpper->eOperator & mask) ? a[1] : 0);

        ** then use the probability provided by the application. */
        pLoop->nOut += pTerm->truthProb;
      }else{
        /* In the absence of explicit truth probabilities, use heuristics to
        ** guess a reasonable truth probability. */
        pLoop->nOut--;
        if( pTerm->eOperator&(WO_EQ|WO_IS) ){
          Expr *pRight;
          assert( pTerm->pExpr->eX==EX_Right );
          pRight = pTerm->pExpr->x.pRight;
          testcase( pTerm->pExpr->op==TK_IS );
          if( sqlite3ExprIsInteger(pRight, &k) && k>=(-1) && k<=1 ){
            k = 10;
          }else{
            k = 20;
          }
          if( iReduce<k ) iReduce = k;

  nCmp = MIN(nCmp, (pIdx->nColumn - nEq));
  for(i=1; i<nCmp; i++){
    /* Test if comparison i of pTerm is compatible with column (i+nEq) 
    ** of the index. If not, exit the loop.  */
    char aff;                     /* Comparison affinity */
    char idxaff = 0;              /* Indexed columns affinity */
    CollSeq *pColl;               /* Comparison collation sequence */
    Expr *pLhs;
    Expr *pRhs;
    pLhs = pTerm->pExpr->pLeft->x.pList->a[i].pExpr;
    assert( pTerm->pExpr->eX==EX_Right );
    pRhs = pTerm->pExpr->x.pRight;
    assert( pRhs->eX==EX_Select || pRhs->eX==EX_List );
    if( pRhs->eX==EX_Select ){
      pRhs = pRhs->x.pSelect->pEList->a[i].pExpr;
    }else{
      pRhs = pRhs->x.pList->a[i].pExpr;
    }

    }

    testcase( pLhs->iColumn==XN_ROWID );
    aff = sqlite3CompareAffinity(pRhs, sqlite3ExprAffinity(pLhs));
    idxaff = sqlite3TableColumnAffinity(pIdx->pTable, pLhs->iColumn);
    if( aff!=idxaff ) break;

    pColl = sqlite3ComparisonCollSeq(pParse, pLhs, pRhs);
    if( pColl==0 ) break;
    if( sqlite3StrICmp(pColl->zName, pIdx->azColl[i+nEq]) ) break;
  }
  return i;
}

/*

        if( nInMul==0 
         && pProbe->nSample 
         && pNew->u.btree.nEq<=pProbe->nSampleCol
         && ((eOp & WO_IN)==0 || pTerm->pExpr->eX==EX_List)
         && OptimizationEnabled(db, SQLITE_Stat34)
        ){
          Expr *pExpr = pTerm->pExpr;
          if( (eOp & (WO_EQ|WO_IS))!=0 ){
            testcase( eOp & WO_EQ );
            testcase( eOp & WO_IS );
            testcase( eOp & WO_ISNULL );
            assert( pExpr->eX==EX_Right );
            rc = whereEqualScanEst(pParse, pBuilder, pExpr->x.pRight, &nOut);
          }else if( pExpr->eX==EX_List ){
            rc = whereInScanEst(pParse, pBuilder, pExpr->x.pList, &nOut);
          }
          if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK;
          if( rc!=SQLITE_OK ) break;          /* Jump out of the pTerm loop */
          if( nOut ){
            pNew->nOut = sqlite3LogEst(nOut);
            if( pNew->nOut>saved_nOut ) pNew->nOut = saved_nOut;

*/
static int whereUsablePartialIndex(int iTab, WhereClause *pWC, Expr *pWhere){
  int i;
  WhereTerm *pTerm;
  Parse *pParse = pWC->pWInfo->pParse;
  while( pWhere->op==TK_AND ){
    if( !whereUsablePartialIndex(iTab,pWC,pWhere->pLeft) ) return 0;
    assert( pWhere->eX==EX_Right );
    pWhere = pWhere->x.pRight;
  }
  if( pParse->db->flags & SQLITE_EnableQPSG ) pParse = 0;
  for(i=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
    Expr *pExpr = pTerm->pExpr;
    if( (!ExprHasProperty(pExpr, EP_FromJoin) || pExpr->iRightJoinTable==iTab)
     && sqlite3ExprImpliesExpr(pParse, pExpr, pWhere, iTab) 
    ){

  HiddenIndexInfo *pHidden = (HiddenIndexInfo*)&pIdxInfo[1];
  const char *zRet = 0;
  if( iCons>=0 && iCons<pIdxInfo->nConstraint ){
    CollSeq *pC = 0;
    int iTerm = pIdxInfo->aConstraint[iCons].iTermOffset;
    Expr *pX = pHidden->pWC->a[iTerm].pExpr;
    if( pX->pLeft ){
      pC = sqlite3ComparisonExprCollSeq(pHidden->pParse,pX);
    }
    zRet = (pC ? pC->zName : sqlite3StrBINARY);
  }
  return zRet;
}

/*

  Expr *pX = pTerm->pExpr;
  Vdbe *v = pParse->pVdbe;
  int iReg;                  /* Register holding results */

  assert( pLevel->pWLoop->aLTerm[iEq]==pTerm );
  assert( iTarget>0 );
  if( pX->op==TK_EQ || pX->op==TK_IS ){
    assert( pX->eX==EX_Right );
    iReg = sqlite3ExprCodeTarget(pParse, pX->x.pRight, iTarget);
  }else if( pX->op==TK_ISNULL ){
    iReg = iTarget;
    sqlite3VdbeAddOp2(v, OP_Null, 0, iReg);
#ifndef SQLITE_OMIT_SUBQUERY
  }else{
    int eType = IN_INDEX_NOOP;
    int iTab;

        /* No affinity ever needs to be (or should be) applied to a value
        ** from the RHS of an "? IN (SELECT ...)" expression. The 
        ** sqlite3FindInIndex() routine has already ensured that the 
        ** affinity of the comparison has been applied to the value.  */
        if( zAff ) zAff[j] = SQLITE_AFF_BLOB;
      }
    }else if( (pTerm->eOperator & WO_ISNULL)==0 ){
      Expr *pRight;
      assert( pTerm->pExpr->eX==EX_Right );
      pRight = pTerm->pExpr->x.pRight;
      if( (pTerm->wtFlags & TERM_IS)==0 && sqlite3ExprCanBeNull(pRight) ){
        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+j, pLevel->addrBrk);
        VdbeCoverage(v);
      }
      if( zAff ){
        if( sqlite3CompareAffinity(pRight, zAff[j])==SQLITE_AFF_BLOB ){
          zAff[j] = SQLITE_AFF_BLOB;

    for(j=0; j<nConstraint; j++){
      int iTarget = iReg+j+2;
      pTerm = pLoop->aLTerm[j];
      if( NEVER(pTerm==0) ) continue;
      if( pTerm->eOperator & WO_IN ){
        codeEqualityTerm(pParse, pTerm, pLevel, j, bRev, iTarget);
        addrNotFound = pLevel->addrNxt;
      }else if( pTerm->pExpr->eX==EX_Right ){
        Expr *pRight;
        pRight = pTerm->pExpr->x.pRight;
        codeExprOrVector(pParse, pRight, iTarget, 1);
      }
    }
    sqlite3VdbeAddOp2(v, OP_Integer, pLoop->u.vtab.idxNum, iReg);
    sqlite3VdbeAddOp2(v, OP_Integer, nConstraint, iReg+1);
    sqlite3VdbeAddOp4(v, OP_VFilter, iCur, addrNotFound, iReg,
                      pLoop->u.vtab.idxStr,

        /* Generate code that will continue to the next row if 
        ** the IN constraint is not satisfied */
        pCompare = sqlite3PExpr(pParse, TK_EQ, 0, 0);
        assert( pCompare!=0 || db->mallocFailed );
        if( pCompare ){
          pCompare->pLeft = pTerm->pExpr->pLeft;
          assert( pCompare->eX==EX_None );
          pRight = sqlite3Expr(db, TK_REGISTER, 0);
          if( pRight ){
            pCompare->x.pRight = pRight;
            pCompare->eX = EX_Right;
            pRight->iTable = iReg+j+2;
            sqlite3ExprIfFalse(pParse, pCompare, pLevel->addrCont, 0);
          }
          pCompare->pLeft = 0;
          sqlite3ExprDelete(db, pCompare);
        }
      }

      assert( TK_GE==TK_GT+3 );      /*  ... is correcct. */

      assert( (pStart->wtFlags & TERM_VNULL)==0 );
      testcase( pStart->wtFlags & TERM_VIRTUAL );
      pX = pStart->pExpr;
      assert( pX!=0 );
      testcase( pStart->leftCursor!=iCur ); /* transitive constraints */
      assert( pX->eX==EX_Right );
      if( sqlite3ExprIsVector(pX->x.pRight) ){
        r1 = rTemp = sqlite3GetTempReg(pParse);
        codeExprOrVector(pParse, pX->x.pRight, r1, 1);
        testcase( pX->op==TK_GT );
        testcase( pX->op==TK_GE );
        testcase( pX->op==TK_LT );
        testcase( pX->op==TK_LE );
        op = aMoveOp[((pX->op - TK_GT - 1) & 0x3) | 0x1];
        assert( pX->op!=TK_GT || op==OP_SeekGE );
        assert( pX->op!=TK_GE || op==OP_SeekGE );
        assert( pX->op!=TK_LT || op==OP_SeekLE );
        assert( pX->op!=TK_LE || op==OP_SeekLE );
      }else{
        r1 = sqlite3ExprCodeTemp(pParse, pX->x.pRight, &rTemp);
        disableTerm(pLevel, pStart);
        op = aMoveOp[(pX->op - TK_GT)];
      }
      sqlite3VdbeAddOp3(v, op, iCur, addrBrk, r1);
      VdbeComment((v, "pk"));
      VdbeCoverageIf(v, pX->op==TK_GT);
      VdbeCoverageIf(v, pX->op==TK_LE);
      VdbeCoverageIf(v, pX->op==TK_LT);
      VdbeCoverageIf(v, pX->op==TK_GE);
      sqlite3ReleaseTempReg(pParse, rTemp);
    }else{
      sqlite3VdbeAddOp2(v, bRev ? OP_Last : OP_Rewind, iCur, addrHalt);
      VdbeCoverageIf(v, bRev==0);
      VdbeCoverageIf(v, bRev!=0);
    }
    if( pEnd ){
      Expr *pX;
      pX = pEnd->pExpr;
      assert( pX!=0 );
      assert( pX->eX==EX_Right );
      assert( (pEnd->wtFlags & TERM_VNULL)==0 );
      testcase( pEnd->leftCursor!=iCur ); /* Transitive constraints */
      testcase( pEnd->wtFlags & TERM_VIRTUAL );
      memEndValue = ++pParse->nMem;
      codeExprOrVector(pParse, pX->x.pRight, memEndValue, 1);
      if( 0==sqlite3ExprIsVector(pX->x.pRight) 
       && (pX->op==TK_LT || pX->op==TK_GT) 
      ){
        testOp = bRev ? OP_Le : OP_Ge;
      }else{
        testOp = bRev ? OP_Lt : OP_Gt;
      }
      if( 0==sqlite3ExprIsVector(pX->x.pRight) ){
        disableTerm(pLevel, pEnd);
      }
    }
    start = sqlite3VdbeCurrentAddr(v);
    pLevel->op = bRev ? OP_Prev : OP_Next;
    pLevel->p1 = iCur;
    pLevel->p2 = start;

    startEq = !pRangeStart || pRangeStart->eOperator & (WO_LE|WO_GE);
    endEq =   !pRangeEnd || pRangeEnd->eOperator & (WO_LE|WO_GE);
    start_constraints = pRangeStart || nEq>0;

    /* Seek the index cursor to the start of the range. */
    nConstraint = nEq;
    if( pRangeStart ){
      Expr *pRight;
      assert( pRangeStart->pExpr->eX==EX_Right );
      pRight = pRangeStart->pExpr->x.pRight;
      codeExprOrVector(pParse, pRight, regBase+nEq, nBtm);
      whereLikeOptimizationStringFixup(v, pLevel, pRangeStart);
      if( (pRangeStart->wtFlags & TERM_VNULL)==0
       && sqlite3ExprCanBeNull(pRight)
      ){
        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
        VdbeCoverage(v);

    }

    /* Load the value for the inequality constraint at the end of the
    ** range (if any).
    */
    nConstraint = nEq;
    if( pRangeEnd ){
      Expr *pRight;
      assert( pRangeEnd->pExpr->eX==EX_Right );
      pRight = pRangeEnd->pExpr->x.pRight;
      codeExprOrVector(pParse, pRight, regBase+nEq, nTop);
      whereLikeOptimizationStringFixup(v, pLevel, pRangeEnd);
      if( (pRangeEnd->wtFlags & TERM_VNULL)==0
       && sqlite3ExprCanBeNull(pRight)
      ){
        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
        VdbeCoverage(v);

** that the collating sequence does not change.  For example:
** "Y collate NOCASE op X" becomes "X op Y" because any collation sequence on
** the left hand side of a comparison overrides any collation sequence 
** attached to the right. For the same reason the EP_Collate flag
** is not commuted.
*/
static void exprCommute(Parse *pParse, Expr *pExpr){
  u16 expRight, expLeft;
  assert( pExpr->eX==EX_Right );
  expRight = (pExpr->x.pRight->flags & EP_Collate);
  expLeft = (pExpr->pLeft->flags & EP_Collate);
  assert( allowedOp(pExpr->op) && pExpr->op!=TK_IN );
  if( expRight==expLeft ){
    /* Either X and Y both have COLLATE operator or neither do */
    if( expRight ){
      /* Both X and Y have COLLATE operators.  Make sure X is always
      ** used by clearing the EP_Collate flag from Y. */
      pExpr->x.pRight->flags &= ~EP_Collate;
    }else if( sqlite3ExprCollSeq(pParse, pExpr->pLeft)!=0 ){
      /* Neither X nor Y have COLLATE operators, but X has a non-default
      ** collating sequence.  So add the EP_Collate marker on X to cause
      ** it to be searched first. */
      pExpr->pLeft->flags |= EP_Collate;
    }
  }
  SWAP(Expr*,pExpr->x.pRight,pExpr->pLeft);
  if( pExpr->op>=TK_GT ){
    assert( TK_LT==TK_GT+2 );
    assert( TK_GE==TK_LE+2 );
    assert( TK_GT>TK_EQ );
    assert( TK_GT<TK_LE );
    assert( pExpr->op>=TK_GT && pExpr->op<=TK_GE );
    pExpr->op = ((pExpr->op-TK_GT)^2)+TK_GT;

          return 1;
        }
      }
    }
  }else if( pExpr->op==TK_NE || pExpr->op==TK_ISNOT || pExpr->op==TK_NOTNULL ){
    int res = 0;
    Expr *pLeft = pExpr->pLeft;
    Expr *pRight = pExpr->x.pRight;
    if( pLeft->op==TK_COLUMN && IsVirtual(pLeft->pTab) ){
      res++;
    }
    if( pRight && pRight->op==TK_COLUMN && IsVirtual(pRight->pTab) ){
      res++;
      SWAP(Expr*, pLeft, pRight);
    }

  int op;                /* Operator for the combined expression */
  int idxNew;            /* Index in pWC of the next virtual term */

  if( (pOne->eOperator & (WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE))==0 ) return;
  if( (pTwo->eOperator & (WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE))==0 ) return;
  if( (eOp & (WO_EQ|WO_LT|WO_LE))!=eOp
   && (eOp & (WO_EQ|WO_GT|WO_GE))!=eOp ) return;
  assert( pOne->pExpr->pLeft!=0 && pOne->pExpr->eX==EX_Right );
  assert( pTwo->pExpr->pLeft!=0 && pTwo->pExpr->eX==EX_Right );
  if( sqlite3ExprCompare(0,pOne->pExpr->pLeft, pTwo->pExpr->pLeft, -1) ){
    return;
  }
  if( sqlite3ExprCompare(0,pOne->pExpr->x.pRight, pTwo->pExpr->x.pRight,-1) ){
    return;
  }
  /* If we reach this point, it means the two subterms can be combined */
  if( (eOp & (eOp-1))!=0 ){
    if( eOp & (WO_LT|WO_LE) ){
      eOp = WO_LE;
    }else{
      assert( eOp & (WO_GT|WO_GE) );
      eOp = WO_GE;

          okToChngToIN = 0;
        }else{
          int affLeft, affRight;
          /* If the right-hand side is also a column, then the affinities
          ** of both right and left sides must be such that no type
          ** conversions are required on the right.  (Ticket #2249)
          */
          assert( pOrTerm->pExpr->eX==EX_Right );
          affRight = sqlite3ExprAffinity(pOrTerm->pExpr->x.pRight);
          affLeft = sqlite3ExprAffinity(pOrTerm->pExpr->pLeft);
          if( affRight!=0 && affRight!=affLeft ){
            okToChngToIN = 0;
          }else{
            pOrTerm->wtFlags |= TERM_OR_OK;
          }
        }

      Expr *pNew;            /* The complete IN operator */

      for(i=pOrWc->nTerm-1, pOrTerm=pOrWc->a; i>=0; i--, pOrTerm++){
        if( (pOrTerm->wtFlags & TERM_OR_OK)==0 ) continue;
        assert( pOrTerm->eOperator & WO_EQ );
        assert( pOrTerm->leftCursor==iCursor );
        assert( pOrTerm->u.leftColumn==iColumn );
        assert( pOrTerm->pExpr->eX==EX_Right );
        pDup = sqlite3ExprDup(db, pOrTerm->pExpr->x.pRight, 0);
        pList = sqlite3ExprListAppend(pWInfo->pParse, pList, pDup);
        pLeft = pOrTerm->pExpr->pLeft;
      }
      assert( pLeft!=0 );
      pDup = sqlite3ExprDup(db, pLeft, 0);
      pNew = sqlite3PExpr(pParse, TK_IN, pDup, 0);
      if( pNew && pList ){

static int termIsEquivalence(Parse *pParse, Expr *pExpr){
  char aff1, aff2;
  CollSeq *pColl;
  if( !OptimizationEnabled(pParse->db, SQLITE_Transitive) ) return 0;
  if( pExpr->op!=TK_EQ && pExpr->op!=TK_IS ) return 0;
  if( ExprHasProperty(pExpr, EP_FromJoin) ) return 0;
  aff1 = sqlite3ExprAffinity(pExpr->pLeft);
  assert( pExpr->eX==EX_Right );
  aff2 = sqlite3ExprAffinity(pExpr->x.pRight);
  if( aff1!=aff2
   && (!sqlite3IsNumericAffinity(aff1) || !sqlite3IsNumericAffinity(aff2))
  ){
    return 0;
  }
  pColl = sqlite3ComparisonExprCollSeq(pParse, pExpr);
  if( sqlite3IsBinary(pColl) ) return 1;
  return sqlite3ExprCollSeqMatch(pParse, pExpr->pLeft, pExpr->x.pRight);
}

/*
** Recursively walk the expressions of a SELECT statement and generate
** a bitmask indicating which tables are used in that expression
** tree.
*/

  pTerm = &pWC->a[idxTerm];
  pMaskSet = &pWInfo->sMaskSet;
  pExpr = pTerm->pExpr;
  assert( pExpr->op!=TK_AS && pExpr->op!=TK_COLLATE );
  prereqLeft = sqlite3WhereExprUsage(pMaskSet, pExpr->pLeft);
  op = pExpr->op;
  if( op==TK_IN ){
    assert( pExpr->eX!=EX_Right );
    if( sqlite3ExprCheckIN(pParse, pExpr) ) return;
    switch( pExpr->eX ){
      case EX_Select: {
        pTerm->prereqRight = exprSelectUsage(pMaskSet, pExpr->x.pSelect);
        break;
      }
      case EX_List: {
        pTerm->prereqRight = sqlite3WhereExprListUsage(pMaskSet,pExpr->x.pList);
        break;
      }
    }
  }else{
    assert( op!=TK_ISNULL || pExpr->eX!=EX_Right );
    if( pExpr->eX==EX_Right ){
      pTerm->prereqRight = sqlite3WhereExprUsage(pMaskSet, pExpr->x.pRight);
    }else{
      pTerm->prereqRight = 0;
    }
  }
  pMaskSet->bVarSelect = 0;
  prereqAll = sqlite3WhereExprUsageNN(pMaskSet, pExpr);
  if( pMaskSet->bVarSelect ) pTerm->wtFlags |= TERM_VARSELECT;
  if( ExprHasProperty(pExpr, EP_FromJoin) ){
    Bitmask x = sqlite3WhereGetMask(pMaskSet, pExpr->iRightJoinTable);
    prereqAll |= x;
    extraRight = x-1;  /* ON clause terms may not be used with an index
                       ** on left table of a LEFT JOIN.  Ticket #3015 */
    if( (prereqAll>>1)>=x ){
      sqlite3ErrorMsg(pParse, "ON clause references tables to its right");
      return;
    }
  }
  pTerm->prereqAll = prereqAll;
  pTerm->leftCursor = -1;
  pTerm->iParent = -1;
  pTerm->eOperator = 0;
  if( allowedOp(op) ){
    int aiCurCol[2];
    Expr *pLeft, *pRight;
    u16 opMask;

    pLeft = sqlite3ExprSkipCollate(pExpr->pLeft);
    if( pExpr->eX==EX_Right ){
      pRight = sqlite3ExprSkipCollate(pExpr->x.pRight);
    }else{
      pRight = 0;
    }
    opMask = (pTerm->prereqRight & prereqLeft)==0 ? WO_ALL : WO_EQUIV;
    if( pTerm->iField>0 ){
      assert( op==TK_IN );
      assert( pLeft->op==TK_VECTOR );
      pLeft = pLeft->x.pList->a[pTerm->iField-1].pExpr;
    }

    if( exprMightBeIndexed(pSrc, prereqLeft, aiCurCol, pLeft, op) ){

  ** no longer used.
  **
  ** This is only required if at least one side of the comparison operation
  ** is not a sub-select.  */
  if( pWC->op==TK_AND 
  && (pExpr->op==TK_EQ || pExpr->op==TK_IS)
  && (nLeft = sqlite3ExprVectorSize(pExpr->pLeft))>1
  && ALWAYS(pExpr->eX==EX_Right)
  && sqlite3ExprVectorSize(pExpr->x.pRight)==nLeft
  && ( pExpr->pLeft->eX!=EX_Select || pExpr->x.pRight->eX!=EX_Select )
  ){
    int i;
    for(i=0; i<nLeft; i++){
      int idxNew;
      Expr *pNew, *pLeft, *pRight;

      pLeft = sqlite3ExprForVectorField(pParse, pExpr->pLeft, i);
      assert( pExpr->eX==EX_Right );
      pRight = sqlite3ExprForVectorField(pParse, pExpr->x.pRight, i);

      pNew = sqlite3PExpr(pParse, pExpr->op, pLeft, pRight);
      transferJoinMarkings(pNew, pExpr);
      idxNew = whereClauseInsert(pWC, pNew, TERM_DYNAMIC);
      exprAnalyze(pSrc, pWC, idxNew);
    }
    pTerm = &pWC->a[idxTerm];
    pTerm->wtFlags |= TERM_CODED|TERM_VIRTUAL;  /* Disable the original */

void sqlite3WhereSplit(WhereClause *pWC, Expr *pExpr, u8 op){
  Expr *pE2 = sqlite3ExprSkipCollate(pExpr);
  pWC->op = op;
  if( pE2==0 ) return;
  if( pE2->op!=op ){
    whereClauseInsert(pWC, pExpr, 0);
  }else{
    assert( pE2->eX==EX_Right );
    sqlite3WhereSplit(pWC, pE2->pLeft, op);
    sqlite3WhereSplit(pWC, pE2->x.pRight, op);
  }
}

/*
** Initialize a preallocated WhereClause structure.
*/
void sqlite3WhereClauseInit(

    return sqlite3WhereGetMask(pMaskSet, p->iTable);
  }else if( ExprHasProperty(p, EP_TokenOnly|EP_Leaf) ){
    assert( p->op!=TK_IF_NULL_ROW );
    return 0;
  }
  mask = (p->op==TK_IF_NULL_ROW) ? sqlite3WhereGetMask(pMaskSet, p->iTable) : 0;
  if( p->pLeft ) mask |= sqlite3WhereExprUsageNN(pMaskSet, p->pLeft);
  switch( p->eX ){
    case EX_Right: {
      mask |= sqlite3WhereExprUsageNN(pMaskSet, p->x.pRight);

      break;

    }
    case EX_Select: {
      if( ExprHasProperty(p, EP_VarSelect) ) pMaskSet->bVarSelect = 1;
      mask |= exprSelectUsage(pMaskSet, p->x.pSelect);
      break;
    }
    case EX_List: {
      mask |= sqlite3WhereExprListUsage(pMaskSet, p->x.pList);
      break;

    }
  }
  return mask;
}
Bitmask sqlite3WhereExprUsage(WhereMaskSet *pMaskSet, Expr *p){
  return p ? sqlite3WhereExprUsageNN(pMaskSet,p) : 0;
}