SQLite

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

















/*
** 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 = sqlite3BinaryCompareCollSeq(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 *pRight = pExpr->pRight;
  int nLeft = sqlite3ExprVectorSize(pLeft);
  int i;
  int regLeft = 0;
  int regRight = 0;
  u8 opx = op;
  int addrDone = sqlite3VdbeMakeLabel(pParse);


  if( nLeft!=sqlite3ExprVectorSize(pRight) ){
    sqlite3ErrorMsg(pParse, "row value misused");
    return;
  }
  assert( pExpr->op==TK_EQ || pExpr->op==TK_NE 
       || pExpr->op==TK_IS || pExpr->op==TK_ISNOT 

  for(i=0; 1 /*Loop exits by "break"*/; i++){
    int regFree1 = 0, regFree2 = 0;
    Expr *pL, *pR; 
    int r1, r2;
    assert( i>=0 && i<nLeft );
    r1 = exprVectorRegister(pParse, pLeft, i, regLeft, &pL, &regFree1);
    r2 = exprVectorRegister(pParse, pRight, i, regRight, &pR, &regFree2);
    codeCompare(pParse, pL, pR, opx, r1, r2, dest, p5);
    testcase(op==OP_Lt); VdbeCoverageIf(v,op==OP_Lt);
    testcase(op==OP_Le); VdbeCoverageIf(v,op==OP_Le);
    testcase(op==OP_Gt); VdbeCoverageIf(v,op==OP_Gt);
    testcase(op==OP_Ge); VdbeCoverageIf(v,op==OP_Ge);
    testcase(op==OP_Eq); VdbeCoverageIf(v,op==OP_Eq);
    testcase(op==OP_Ne); VdbeCoverageIf(v,op==OP_Ne);
    sqlite3ReleaseTempReg(pParse, regFree1);

      Expr *pLeft = pExpr->pLeft;
      if( sqlite3ExprIsVector(pLeft) ){
        codeVectorCompare(pParse, pExpr, target, op, p5);
      }else{
        r1 = sqlite3ExprCodeTemp(pParse, pLeft, &regFree1);
        r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, &regFree2);
        codeCompare(pParse, pLeft, pExpr->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);
        testcase( regFree1==0 );

    case TK_NE:
    case TK_EQ: {
      if( sqlite3ExprIsVector(pExpr->pLeft) ) goto default_expr;
      testcase( jumpIfNull==0 );
      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
      r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, &regFree2);
      codeCompare(pParse, pExpr->pLeft, pExpr->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);
      VdbeCoverageIf(v, op==OP_Eq && jumpIfNull!=SQLITE_NULLEQ);

    case TK_NE:
    case TK_EQ: {
      if( sqlite3ExprIsVector(pExpr->pLeft) ) goto default_expr;
      testcase( jumpIfNull==0 );
      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
      r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, &regFree2);
      codeCompare(pParse, pExpr->pLeft, pExpr->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);
      VdbeCoverageIf(v, op==OP_Eq && jumpIfNull==SQLITE_NULLEQ);

      return 0;
    }else if( pA->op==TK_COLLATE ){
      if( sqlite3_stricmp(pA->u.zToken,pB->u.zToken)!=0 ) return 2;
    }else if( ALWAYS(pB->u.zToken!=0) && strcmp(pA->u.zToken,pB->u.zToken)!=0 ){
      return 2;
    }
  }
  if( (pA->flags & EP_Distinct)!=(pB->flags & EP_Distinct) ) return 2;

  if( (combinedFlags & EP_TokenOnly)==0 ){
    if( combinedFlags & EP_xIsSelect ) return 2;
    if( (combinedFlags & EP_FixedCol)==0
     && sqlite3ExprCompare(pParse, pA->pLeft, pB->pLeft, iTab) ) return 2;
    if( sqlite3ExprCompare(pParse, pA->pRight, pB->pRight, iTab) ) return 2;
    if( sqlite3ExprListCompare(pA->x.pList, pB->x.pList, iTab) ) return 2;
    if( pA->op!=TK_STRING

  pRight = pExpr->pRight;
  pLeft = pExpr->pLeft;
  assert( pRight!=0 );
  assert( pLeft!=0 );
  if( pRight->op==TK_COLUMN
   && !ExprHasProperty(pRight, EP_FixedCol)
   && sqlite3ExprIsConstant(pLeft)
   && sqlite3IsBinary(sqlite3BinaryCompareCollSeq(pConst->pParse,pLeft,pRight))
  ){
    constInsert(pConst, pRight, pLeft);
  }else
  if( pLeft->op==TK_COLUMN
   && !ExprHasProperty(pLeft, EP_FixedCol)
   && sqlite3ExprIsConstant(pRight)
   && sqlite3IsBinary(sqlite3BinaryCompareCollSeq(pConst->pParse,pLeft,pRight))
  ){
    constInsert(pConst, pLeft, pRight);
  }
}

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

#define EP_HasFunc    0x000004 /* Contains one or more functions of any kind */
#define EP_FixedCol   0x000008 /* TK_Column with a known fixed value */
#define EP_Agg        0x000010 /* Contains one or more aggregate functions */
#define EP_VarSelect  0x000020 /* pSelect is correlated, not constant */
#define EP_DblQuoted  0x000040 /* token.z was originally in "..." */
#define EP_InfixFunc  0x000080 /* True for an infix function: LIKE, GLOB, etc */
#define EP_Collate    0x000100 /* Tree contains a TK_COLLATE operator */
  /*                  0x000200 Available for reuse */
#define EP_IntValue   0x000400 /* Integer value contained in u.iValue */
#define EP_xIsSelect  0x000800 /* x.pSelect is valid (otherwise x.pList is) */
#define EP_Skip       0x001000 /* Operator does not contribute to affinity */
#define EP_Reduced    0x002000 /* Expr struct EXPR_REDUCEDSIZE bytes only */
#define EP_TokenOnly  0x004000 /* Expr struct EXPR_TOKENONLYSIZE bytes only */
#define EP_Win        0x008000 /* Contains window functions */
#define EP_MemToken   0x010000 /* Need to sqlite3DbFree() Expr.zToken */

int sqlite3TransferBindings(sqlite3_stmt *, sqlite3_stmt *);
void sqlite3ParserReset(Parse*);
#ifdef SQLITE_ENABLE_NORMALIZE
char *sqlite3Normalize(Vdbe*, const char*);
#endif
int sqlite3Reprepare(Vdbe*);
void sqlite3ExprListCheckLength(Parse*, ExprList*, const char*);

CollSeq *sqlite3BinaryCompareCollSeq(Parse *, Expr *, 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

              CollSeq *pColl;
              Parse *pParse = pWC->pWInfo->pParse;
              pX = pTerm->pExpr;
              if( !sqlite3IndexAffinityOk(pX, pScan->idxaff) ){
                continue;
              }
              assert(pX->pLeft);
              pColl = sqlite3BinaryCompareCollSeq(pParse,
                                                  pX->pLeft, pX->pRight);
              if( pColl==0 ) pColl = pParse->db->pDfltColl;
              if( sqlite3StrICmp(pColl->zName, pScan->zCollName) ){
                continue;
              }
            }
            if( (pTerm->eOperator & (WO_EQ|WO_IS))!=0
             && (pX = pTerm->pExpr->pRight)->op==TK_COLUMN

      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 = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
        pIdx->azColl[n] = pColl ? pColl->zName : sqlite3StrBINARY;
        n++;
      }
    }
  }
  assert( (u32)n==pLoop->u.btree.nEq );

  /* Add additional columns needed to make the automatic index into

  while( pWhere->op==TK_AND ){
    if( !whereUsablePartialIndex(iTab,pWC,pWhere->pLeft) ) return 0;
    pWhere = pWhere->pRight;
  }
  if( pParse->db->flags & SQLITE_EnableQPSG ) pParse = 0;
  for(i=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
    Expr *pExpr;
    if( pTerm->wtFlags & TERM_NOPARTIDX ) continue;
    pExpr = pTerm->pExpr;
    if( (!ExprHasProperty(pExpr, EP_FromJoin) || pExpr->iRightJoinTable==iTab)
     && sqlite3ExprImpliesExpr(pParse, pExpr, pWhere, iTab) 
    ){
      return 1;
    }
  }

  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 = sqlite3BinaryCompareCollSeq(pHidden->pParse, pX->pLeft, pX->pRight);
    }
    zRet = (pC ? pC->zName : sqlite3StrBINARY);
  }
  return zRet;
}

/*

#  define TERM_VNULL    0x00   /* Disabled if not using stat4 */
#endif
#define TERM_LIKEOPT    0x100  /* Virtual terms from the LIKE optimization */
#define TERM_LIKECOND   0x200  /* Conditionally this LIKE operator term */
#define TERM_LIKE       0x400  /* The original LIKE operator */
#define TERM_IS         0x800  /* Term.pExpr is an IS operator */
#define TERM_VARSELECT  0x1000 /* Term.pExpr contains a correlated sub-query */
#define TERM_NOPARTIDX  0x2000 /* Not for use to enable a partial index */

/*
** An instance of the WhereScan object is used as an iterator for locating
** terms in the WHERE clause that are useful to the query planner.
*/
struct WhereScan {
  WhereClause *pOrigWC;      /* Original, innermost WhereClause */

  assert( TK_GE==TK_EQ+4 );
  return op==TK_IN || (op>=TK_EQ && op<=TK_GE) || op==TK_ISNULL || op==TK_IS;
}

/*
** Commute a comparison operator.  Expressions of the form "X op Y"
** are converted into "Y op X".
**
** If left/right precedence rules come into play when determining the
** collating sequence, then COLLATE operators are adjusted to ensure
** 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.
**
** The return value is extra flags that are added to the WhereTerm object
** after it is commuted.  The only extra flag ever added is TERM_NOPARTIDX
** which prevents the term from being used to enable a partial index if
** COLLATE changes have been made.
*/
static u16 exprCommute(Parse *pParse, Expr *pExpr){
  u16 expRight = (pExpr->pRight->flags & EP_Collate);
  u16 expLeft = (pExpr->pLeft->flags & EP_Collate);
  u16 wtFlags = 0;
  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->pRight->flags &= ~EP_Collate;
      wtFlags |= TERM_NOPARTIDX;
    }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;
      wtFlags |= TERM_NOPARTIDX;
    }
  }
  SWAP(Expr*,pExpr->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 wtFlags;
}

/*
** Translate from TK_xx operator to WO_xx bitmask.
*/
static u16 operatorMask(int op){
  u16 c;

  aff1 = sqlite3ExprAffinity(pExpr->pLeft);
  aff2 = sqlite3ExprAffinity(pExpr->pRight);
  if( aff1!=aff2
   && (!sqlite3IsNumericAffinity(aff1) || !sqlite3IsNumericAffinity(aff2))
  ){
    return 0;
  }
  pColl = sqlite3BinaryCompareCollSeq(pParse, pExpr->pLeft, pExpr->pRight);
  if( sqlite3IsBinary(pColl) ) return 1;
  return sqlite3ExprCollSeqMatch(pParse, pExpr->pLeft, pExpr->pRight);
}

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