SQLite

    if( (pTerm->eOperator & ~(WO_EQUIV))==0 ) continue;
    if( pTerm->wtFlags & TERM_VNULL ) continue;
    assert( pTerm->u.leftColumn>=(-1) );
    pIdxCons[j].iColumn = pTerm->u.leftColumn;
    pIdxCons[j].iTermOffset = i;
    op = pTerm->eOperator & WO_ALL;
    if( op==WO_IN ) op = WO_EQ;
    if( op==WO_AUX ){
      pIdxCons[j].op = pTerm->eMatchOp;
    }else if( op & (WO_ISNULL|WO_IS) ){
      if( op==WO_ISNULL ){
        pIdxCons[j].op = SQLITE_INDEX_CONSTRAINT_ISNULL;
      }else{
        pIdxCons[j].op = SQLITE_INDEX_CONSTRAINT_IS;
      }
    }else{
      pIdxCons[j].op = (u8)op;
      /* The direct assignment in the previous line is possible only because
      ** the WO_ and SQLITE_INDEX_CONSTRAINT_ codes are identical.  The
      ** following asserts verify this fact. */
      assert( WO_EQ==SQLITE_INDEX_CONSTRAINT_EQ );
      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)
       && sqlite3ExprIsVector(pTerm->pExpr->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;

**
** Value constraints:
**     WO_EQ    == SQLITE_INDEX_CONSTRAINT_EQ
**     WO_LT    == SQLITE_INDEX_CONSTRAINT_LT
**     WO_LE    == SQLITE_INDEX_CONSTRAINT_LE
**     WO_GT    == SQLITE_INDEX_CONSTRAINT_GT
**     WO_GE    == SQLITE_INDEX_CONSTRAINT_GE

*/
#define WO_IN     0x0001
#define WO_EQ     0x0002
#define WO_LT     (WO_EQ<<(TK_LT-TK_EQ))
#define WO_LE     (WO_EQ<<(TK_LE-TK_EQ))
#define WO_GT     (WO_EQ<<(TK_GT-TK_EQ))
#define WO_GE     (WO_EQ<<(TK_GE-TK_EQ))
#define WO_AUX    0x0040       /* Op useful to virtual tables only */
#define WO_IS     0x0080
#define WO_ISNULL 0x0100
#define WO_OR     0x0200       /* Two or more OR-connected terms */
#define WO_AND    0x0400       /* Two or more AND-connected terms */
#define WO_EQUIV  0x0800       /* Of the form A==B, both columns */
#define WO_NOOP   0x1000       /* This term does not restrict search space */

  return rc;
}
#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */


#ifndef SQLITE_OMIT_VIRTUALTABLE
/*
** Check to see if the pExpr expression is a form that needs to be passed
** to the xBestIndex method of virtual tables.  Forms of interest include:
**
**          Expression                   Virtual Table Operator

**          -----------------------      ---------------------------------
**      1.  column MATCH expr            SQLITE_INDEX_CONSTRAINT_MATCH
**      2.  column GLOB expr             SQLITE_INDEX_CONSTRAINT_GLOB
**      3.  column LIKE expr             SQLITE_INDEX_CONSTRAINT_LIKE
**      4.  column REGEXP expr           SQLITE_INDEX_CONSTRAINT_REGEXP

**      5.  column != expr               SQLITE_INDEX_CONSTRAINT_NE
**      6.  expr != column               SQLITE_INDEX_CONSTRAINT_NE
**      7.  column IS NOT expr           SQLITE_INDEX_CONSTRAINT_ISNOT
**      8.  expr IS NOT column           SQLITE_INDEX_CONSTRAINT_ISNOT
**      9.  column IS NOT NULL           SQLITE_INDEX_CONSTRAINT_ISNOTNULL
**
** In every case, "column" must be a column of a virtual table.  If there
** is a match, set *ppLeft to the "column" expression, set *ppRight to the 
** "expr" expression (even though in forms (6) and (8) the column is on the
** right and the expression is on the left).  Also set *peOp2 to the
** appropriate virtual table operator.  The return value is 1 or 2 if there
** is a match.  The usual return is 1, but if the RHS is also a column
** of virtual table in forms (5) or (7) then return 2.
**
** If the expression matches none of the patterns above, return 0.
*/
static int isAuxiliaryVtabOperator(
  Expr *pExpr,                    /* Test this expression */
  unsigned char *peOp2,           /* OUT: 0 for MATCH, or else an op2 value */
  Expr **ppLeft,                  /* Column expression to left of MATCH/op2 */
  Expr **ppRight                  /* Expression to left of MATCH/op2 */
){
  if( pExpr->op==TK_FUNCTION ){
    static const struct Op2 {
      const char *zOp;
      unsigned char eOp2;
    } aOp[] = {
      { "match",  SQLITE_INDEX_CONSTRAINT_MATCH },
      { "glob",   SQLITE_INDEX_CONSTRAINT_GLOB },
      { "like",   SQLITE_INDEX_CONSTRAINT_LIKE },
      { "regexp", SQLITE_INDEX_CONSTRAINT_REGEXP }
    };
    ExprList *pList;
    Expr *pCol;                     /* Column reference */
    int i;




    pList = pExpr->x.pList;
    if( pList==0 || pList->nExpr!=2 ){
      return 0;
    }
    pCol = pList->a[1].pExpr;
    if( pCol->op!=TK_COLUMN || !IsVirtual(pCol->pTab) ){
      return 0;

        sqlite3WhereSplit(pAndWC, pOrTerm->pExpr, TK_AND);
        sqlite3WhereExprAnalyze(pSrc, pAndWC);
        pAndWC->pOuter = pWC;
        if( !db->mallocFailed ){
          for(j=0, pAndTerm=pAndWC->a; j<pAndWC->nTerm; j++, pAndTerm++){
            assert( pAndTerm->pExpr );
            if( allowedOp(pAndTerm->pExpr->op) 
             || pAndTerm->eOperator==WO_AUX
            ){
              b |= sqlite3WhereGetMask(&pWInfo->sMaskSet, pAndTerm->leftCursor);
            }
          }
        }
        indexable &= b;
      }

      markTermAsChild(pWC, idxNew1, idxTerm);
      markTermAsChild(pWC, idxNew2, idxTerm);
    }
  }
#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */

#ifndef SQLITE_OMIT_VIRTUALTABLE
  /* Add a WO_AUX auxiliary term to the constraint set if the
  ** current expression is of the form "column OP expr" where OP
  ** is an operator that gets passed into virtual tables but which is
  ** not normally optimized for ordinary tables.  In other words, OP
  ** is one of MATCH, LIKE, GLOB, REGEXP, !=, IS, IS NOT, or NOT NULL.
  ** This information is used by the xBestIndex methods of
  ** virtual tables.  The native query optimizer does not attempt
  ** to do anything with MATCH functions.
  */
  if( pWC->op==TK_AND ){
    Expr *pRight, *pLeft;

    int res = isAuxiliaryVtabOperator(pExpr, &eOp2, &pLeft, &pRight);
    while( res-- > 0 ){
      int idxNew;
      WhereTerm *pNewTerm;
      Bitmask prereqColumn, prereqExpr;

      prereqExpr = sqlite3WhereExprUsage(pMaskSet, pRight);
      prereqColumn = sqlite3WhereExprUsage(pMaskSet, pLeft);
      if( (prereqExpr & prereqColumn)==0 ){
        Expr *pNewExpr;
        pNewExpr = sqlite3PExpr(pParse, TK_MATCH, 
            0, sqlite3ExprDup(db, pRight, 0));
        if( ExprHasProperty(pExpr, EP_FromJoin) && pNewExpr ){
          ExprSetProperty(pNewExpr, EP_FromJoin);
        }
        idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
        testcase( idxNew==0 );
        pNewTerm = &pWC->a[idxNew];
        pNewTerm->prereqRight = prereqExpr;
        pNewTerm->leftCursor = pLeft->iTable;
        pNewTerm->u.leftColumn = pLeft->iColumn;
        pNewTerm->eOperator = WO_AUX;
        pNewTerm->eMatchOp = eOp2;
        markTermAsChild(pWC, idxNew, idxTerm);
        pTerm = &pWC->a[idxTerm];
        pTerm->wtFlags |= TERM_COPIED;
        pNewTerm->prereqAll = pTerm->prereqAll;
      }
      SWAP(Expr*, pLeft, pRight);