|| sqlite3ExprNeedsNoAffinityChange(p, zAff[i])
    ){
      zAff[i] = SQLITE_AFF_BLOB;
    }
  }
}

#ifdef SQLITE_DEBUG

/* Return true if the pSub ExprList is a subset of pMain.  The terms
** of pSub can be in a different order from pMain.  The only requirement
** is that every term in pSub must exist somewhere in pMain.


**
** Return false if pSub contains any term that is not found in pMain.






















*/
static int exprListSubset(ExprList *pSub, ExprList *pMain){
  int i, j;


















































  for(i=0; i<pSub->nExpr; i++){
    Expr *p = pSub->a[i].pExpr;
    for(j=0; j<pMain->nExpr; j++){
      if( sqlite3ExprCompare(0, p, pMain->a[j].pExpr, 0)==0 ) break;

    }
    if( j>=pMain->nExpr ) return 0;
  }








  return 1;
}
#endif /* SQLITE_DEBUG */


/*
** Generate code for a single equality term of the WHERE clause.  An equality
** term can be either X=expr or X IN (...).   pTerm is the term to be 
** coded.
**
................................................................................
    for(i=0; i<iEq; i++){
      if( pLoop->aLTerm[i] && pLoop->aLTerm[i]->pExpr==pX ){
        disableTerm(pLevel, pTerm);
        return iTarget;
      }
    }
    for(i=iEq;i<pLoop->nLTerm; i++){

      if( ALWAYS(pLoop->aLTerm[i]) && pLoop->aLTerm[i]->pExpr==pX ) nEq++;
    }

    if( (pX->flags & EP_xIsSelect)==0 || pX->x.pSelect->pEList->nExpr==1 ){
      eType = sqlite3FindInIndex(pParse, pX, IN_INDEX_LOOP, 0, 0);
    }else{
      Select *pSelect = pX->x.pSelect;
      sqlite3 *db = pParse->db;
      u16 savedDbOptFlags = db->dbOptFlags;
      ExprList *pOrigRhs = pSelect->pEList;
      ExprList *pOrigLhs = pX->pLeft->x.pList;
      ExprList *pRhs = 0;         /* New Select.pEList for RHS */
      ExprList *pLhs = 0;         /* New pX->pLeft vector */


      for(i=iEq;i<pLoop->nLTerm; i++){
        if( pLoop->aLTerm[i]->pExpr==pX ){
          int iField = pLoop->aLTerm[i]->iField - 1;
          Expr *pNewRhs = sqlite3ExprDup(db, pOrigRhs->a[iField].pExpr, 0);
          Expr *pNewLhs = sqlite3ExprDup(db, pOrigLhs->a[iField].pExpr, 0);

          pRhs = sqlite3ExprListAppend(pParse, pRhs, pNewRhs);
          pLhs = sqlite3ExprListAppend(pParse, pLhs, pNewLhs);
        }
      }
 
      /* pRhs should be a subset of pOrigRhs (though possibly in a different
      ** order).  And pLhs should be a subset of pOrigLhs.  To put it 
      ** another way:  Every term of pRhs should exist in pOrigRhs and
      ** every term of pLhs should exist in pOrigLhs. */
      assert( db->mallocFailed || exprListSubset(pRhs, pOrigRhs) );
      assert( db->mallocFailed || exprListSubset(pLhs, pOrigLhs) );

      if( !db->mallocFailed ){
        Expr *pLeft = pX->pLeft;

        if( pSelect->pOrderBy ){
          /* If the SELECT statement has an ORDER BY clause, zero the 
          ** iOrderByCol variables. These are set to non-zero when an 
          ** ORDER BY term exactly matches one of the terms of the 
          ** result-set. Since the result-set of the SELECT statement may
          ** have been modified or reordered, these variables are no longer 
          ** set correctly.  Since setting them is just an optimization, 
          ** it's easiest just to zero them here.  */
          ExprList *pOrderBy = pSelect->pOrderBy;
          for(i=0; i<pOrderBy->nExpr; i++){
            pOrderBy->a[i].u.x.iOrderByCol = 0;
          }
        }

        /* Take care here not to generate a TK_VECTOR containing only a
        ** single value. Since the parser never creates such a vector, some
        ** of the subroutines do not handle this case.  */
        if( pLhs->nExpr==1 ){
          pX->pLeft = pLhs->a[0].pExpr;
        }else{
          pLeft->x.pList = pLhs;
          aiMap = (int*)sqlite3DbMallocZero(pParse->db, sizeof(int) * nEq);
          testcase( aiMap==0 );
        }
        pSelect->pEList = pRhs;
        db->dbOptFlags |= SQLITE_QueryFlattener;
        eType = sqlite3FindInIndex(pParse, pX, IN_INDEX_LOOP, 0, aiMap);
        db->dbOptFlags = savedDbOptFlags;
        testcase( aiMap!=0 && aiMap[0]!=0 );
        pSelect->pEList = pOrigRhs;
        pLeft->x.pList = pOrigLhs;
        pX->pLeft = pLeft;

      }
      sqlite3ExprListDelete(pParse->db, pLhs);
      sqlite3ExprListDelete(pParse->db, pRhs);


    }

    if( eType==IN_INDEX_INDEX_DESC ){
      testcase( bRev );
      bRev = !bRev;
    }
    iTab = pX->iTable;

     || sqlite3ExprNeedsNoAffinityChange(p, zAff[i])
    ){
      zAff[i] = SQLITE_AFF_BLOB;
    }
  }
}



/*
** pX is an expression of the form:  (vector) IN (SELECT ...)
** In other words, it is a vector IN operator with a SELECT clause on the
** LHS.  But not all terms in the vector are indexable and the terms might
** not be in the correct order for indexing.
**

** This routine makes a copy of the input pX expression and then adjusts
** the vector on the LHS with corresponding changes to the SELECT so that
** the vector contains only index terms and those terms are in the correct
** order.  The modified IN expression is returned.  The caller is responsible
** for deleting the returned expression.
**
** Example:
**
**    CREATE TABLE t1(a,b,c,d,e,f);
**    CREATE INDEX t1x1 ON t1(e,c);
**    SELECT * FROM t1 WHERE (a,b,c,d,e) IN (SELECT v,w,x,y,z FROM t2)
**                           \_______________________________________/
**                                     The pX expression
**
** Since only columns e and c can be used with the index, in that order,
** the modified IN expression that is returned will be:
**
**        (e,c) IN (SELECT z,x FROM t2)
**
** The reduced pX is different from the original (obviously) and thus is
** only used for indexing, to improve performance.  The original unaltered
** IN expression must also be run on each output row for correctness.
*/


static Expr *removeUnindexableInClauseTerms(
  Parse *pParse,        /* The parsing context */
  int iEq,              /* Look at loop terms starting here */
  WhereLoop *pLoop,     /* The current loop */
  Expr *pX              /* The IN expression to be reduced */
){
  sqlite3 *db = pParse->db;
  Expr *pNew = sqlite3ExprDup(db, pX, 0);
  if( db->mallocFailed==0 ){
    ExprList *pOrigRhs = pNew->x.pSelect->pEList;  /* Original unmodified RHS */
    ExprList *pOrigLhs = pNew->pLeft->x.pList;     /* Original unmodified LHS */
    ExprList *pRhs = 0;         /* New RHS after modifications */
    ExprList *pLhs = 0;         /* New LHS after mods */
    int i;                      /* Loop counter */
    Select *pSelect;            /* Pointer to the SELECT on the RHS */

    for(i=iEq; i<pLoop->nLTerm; i++){
      if( pLoop->aLTerm[i]->pExpr==pX ){
        int iField = pLoop->aLTerm[i]->iField - 1;
        assert( pOrigRhs->a[iField].pExpr!=0 );
        pRhs = sqlite3ExprListAppend(pParse, pRhs, pOrigRhs->a[iField].pExpr);
        pOrigRhs->a[iField].pExpr = 0;
        assert( pOrigLhs->a[iField].pExpr!=0 );
        pLhs = sqlite3ExprListAppend(pParse, pLhs, pOrigLhs->a[iField].pExpr);
        pOrigLhs->a[iField].pExpr = 0;
      }
    }
    sqlite3ExprListDelete(db, pOrigRhs);
    sqlite3ExprListDelete(db, pOrigLhs);
    pNew->pLeft->x.pList = pLhs;
    pNew->x.pSelect->pEList = pRhs;
    if( pLhs && pLhs->nExpr==1 ){
      /* Take care here not to generate a TK_VECTOR containing only a
      ** single value. Since the parser never creates such a vector, some
      ** of the subroutines do not handle this case.  */
      Expr *p = pLhs->a[0].pExpr;
      pLhs->a[0].pExpr = 0;
      sqlite3ExprDelete(db, pNew->pLeft);
      pNew->pLeft = p;
    }
    pSelect = pNew->x.pSelect;
    if( pSelect->pOrderBy ){
      /* If the SELECT statement has an ORDER BY clause, zero the 
      ** iOrderByCol variables. These are set to non-zero when an 
      ** ORDER BY term exactly matches one of the terms of the 
      ** result-set. Since the result-set of the SELECT statement may
      ** have been modified or reordered, these variables are no longer 
      ** set correctly.  Since setting them is just an optimization, 
      ** it's easiest just to zero them here.  */
      ExprList *pOrderBy = pSelect->pOrderBy;
      for(i=0; i<pOrderBy->nExpr; i++){



        pOrderBy->a[i].u.x.iOrderByCol = 0;
      }

    }

#if 0
    printf("For indexing, change the IN expr:\n");
    sqlite3TreeViewExpr(0, pX, 0);
    printf("Into:\n");
    sqlite3TreeViewExpr(0, pNew, 0);
#endif
  }
  return pNew;
}



/*
** Generate code for a single equality term of the WHERE clause.  An equality
** term can be either X=expr or X IN (...).   pTerm is the term to be 
** coded.
**
................................................................................
    for(i=0; i<iEq; i++){
      if( pLoop->aLTerm[i] && pLoop->aLTerm[i]->pExpr==pX ){
        disableTerm(pLevel, pTerm);
        return iTarget;
      }
    }
    for(i=iEq;i<pLoop->nLTerm; i++){
      assert( pLoop->aLTerm[i]!=0 );
      if( pLoop->aLTerm[i]->pExpr==pX ) nEq++;
    }

    if( (pX->flags & EP_xIsSelect)==0 || pX->x.pSelect->pEList->nExpr==1 ){
      eType = sqlite3FindInIndex(pParse, pX, IN_INDEX_LOOP, 0, 0);
    }else{

      sqlite3 *db = pParse->db;





      pX = removeUnindexableInClauseTerms(pParse, iEq, pLoop, pX);



















      if( !db->mallocFailed ){























        aiMap = (int*)sqlite3DbMallocZero(pParse->db, sizeof(int)*nEq);




        eType = sqlite3FindInIndex(pParse, pX, IN_INDEX_LOOP, 0, aiMap);





        pTerm->pExpr->iTable = pX->iTable;
      }


      sqlite3ExprDelete(db, pX);
      pX = pTerm->pExpr;
    }

    if( eType==IN_INDEX_INDEX_DESC ){
      testcase( bRev );
      bRev = !bRev;
    }
    iTab = pX->iTable;