SQLite

  WhereCost *pCost            /* Lowest cost query plan */
){
#ifndef SQLITE_OMIT_OR_OPTIMIZATION
  const int iCur = pSrc->iCursor;   /* The cursor of the table to be accessed */
  const Bitmask maskSrc = getMask(pWC->pMaskSet, iCur);  /* Bitmask for pSrc */
  WhereTerm * const pWCEnd = &pWC->a[pWC->nTerm];        /* End of pWC->a[] */
  WhereTerm *pTerm;                 /* A single term of the WHERE clause */

  /* No OR-clause optimization allowed if the NOT INDEXED clause is used */
  if( pSrc->notIndexed ){
    return;
  }

  /* Search the WHERE clause terms for a usable WO_OR term. */
  for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
    if( pTerm->eOperator==WO_OR 
     && ((pTerm->prereqAll & ~maskSrc) & notReady)==0
     && (pTerm->u.pOrInfo->indexable & maskSrc)!=0 
    ){

        used |= sTermCost.used;
        if( rTotal>=pCost->rCost ) break;
      }

      /* If there is an ORDER BY clause, increase the scan cost to account 
      ** for the cost of the sort. */
      if( pOrderBy!=0 ){
        WHERETRACE(("... sorting increases OR cost %.9g to %.9g\n",
                    rTotal, rTotal+nRow*estLog(nRow)));
        rTotal += nRow*estLog(nRow);

      }

      /* If the cost of scanning using this OR term for optimization is
      ** less than the current cost stored in pCost, replace the contents
      ** of pCost. */
      WHERETRACE(("... multi-index OR cost=%.9g nrow=%.9g\n", rTotal, nRow));
      if( rTotal<pCost->rCost ){

    **    the sub-select is assumed to return 25 rows for the purposes of 
    **    determining nInMul.
    **
    **  bInEst:  
    **    Set to true if there was at least one "x IN (SELECT ...)" term used 
    **    in determining the value of nInMul.
    **
    **  estBound:
    **    An estimate on the amount of the table that must be searched.  A
    **    value of 100 means the entire table is searched.  Range constraints
    **    might reduce this to a value less than 100 to indicate that only
    **    a fraction of the table needs searching.  In the absence of
    **    sqlite_stat2 ANALYZE data, a single inequality reduces the search
    **    space to 1/3rd its original size.  So an x>? constraint reduces
    **    estBound to 33.  Two constraints (x>? AND x<?) reduce estBound to 11.
    **
    **  bSort:   
    **    Boolean. True if there is an ORDER BY clause that will require an 
    **    external sort (i.e. scanning the index being evaluated will not 
    **    correctly order records).
    **
    **  bLookup: 

    **
    **             SELECT a, b    FROM tbl WHERE a = 1;
    **             SELECT a, b, c FROM tbl WHERE a = 1;
    */
    int nEq;
    int bInEst = 0;
    int nInMul = 1;
    int estBound = 100;
    int nBound = 0;             /* Number of range constraints seen */
    int bSort = 0;
    int bLookup = 0;
    WhereTerm *pTerm;           /* A single term of the WHERE clause */

    /* Determine the values of nEq and nInMul */
    for(nEq=0; nEq<pProbe->nColumn; nEq++){

      int j = pProbe->aiColumn[nEq];
      pTerm = findTerm(pWC, iCur, j, notReady, eqTermMask, pIdx);
      if( pTerm==0 ) break;
      wsFlags |= (WHERE_COLUMN_EQ|WHERE_ROWID_EQ);
      if( pTerm->eOperator & WO_IN ){
        Expr *pExpr = pTerm->pExpr;
        wsFlags |= WHERE_COLUMN_IN;
        if( ExprHasProperty(pExpr, EP_xIsSelect) ){
          nInMul *= 25;
          bInEst = 1;
        }else if( pExpr->x.pList ){
          nInMul *= pExpr->x.pList->nExpr + 1;
        }
      }else if( pTerm->eOperator & WO_ISNULL ){
        wsFlags |= WHERE_COLUMN_NULL;
      }
      used |= pTerm->prereqRight;
    }

    /* Determine the value of estBound. */
    if( nEq<pProbe->nColumn ){
      int j = pProbe->aiColumn[nEq];
      if( findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE|WO_GT|WO_GE, pIdx) ){
        WhereTerm *pTop = findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE, pIdx);
        WhereTerm *pBtm = findTerm(pWC, iCur, j, notReady, WO_GT|WO_GE, pIdx);
        whereRangeScanEst(pParse, pProbe, nEq, pBtm, pTop, &estBound);
        if( pTop ){
          nBound = 1;
          wsFlags |= WHERE_TOP_LIMIT;
          used |= pTop->prereqRight;
        }
        if( pBtm ){
          nBound++;
          wsFlags |= WHERE_BTM_LIMIT;
          used |= pBtm->prereqRight;
        }
        wsFlags |= (WHERE_COLUMN_RANGE|WHERE_ROWID_RANGE);
      }
    }else if( pProbe->onError!=OE_None ){
      testcase( wsFlags & WHERE_COLUMN_IN );

      if( m==0 ){
        wsFlags |= WHERE_IDX_ONLY;
      }else{
        bLookup = 1;
      }
    }

    /*

    ** Estimate the number of rows of output.  For an IN operator,
    ** do not let the estimate exceed half the rows in the table.
    */
    nRow = (double)(aiRowEst[nEq] * nInMul);
    if( bInEst && nRow*2>aiRowEst[0] ){
      nRow = aiRowEst[0]/2;
      nInMul = (int)(nRow / aiRowEst[nEq]);
    }

    /* Assume constant cost to access a row and logarithmic cost to
    ** do a binary search.  Hence, the initial cost is the number of output
    ** rows plus log2(table-size) times the number of binary searches.
    */
    cost = nRow + nInMul*estLog(aiRowEst[0]);

    /* Adjust the number of rows and the cost downward to reflect rows
    ** that are excluded by range constraints.
    */
    nRow = (nRow * (double)estBound) / (double)100;
    cost = (cost * (double)estBound) / (double)100;

    /* Add in the estimated cost of sorting the result
    */
    if( bSort ){
      cost += cost*estLog(cost);
    }

    /* If all information can be taken directly from the index, we avoid
    ** doing table lookups.  This reduces the cost by half.  (Not really -
    ** this needs to be fixed.)
    */
    if( pIdx && bLookup==0 ){
      cost /= (double)2;
    }
    /**** Cost of using this index has now been computed ****/

    /* If there are additional constraints on this table that cannot
    ** be used with the current index, but which might lower the number
    ** of output rows, adjust the nRow value accordingly.  This only 
    ** matters if the current index is the least costly, so do not bother
    ** with this step if we already know this index will not be chosen.
    ** Also, never reduce the output row count below 2 using this step.
    */
    if( nRow>2 && cost<=pCost->rCost ){
      int k;
      int nSkipEq = nEq;
      int nSkipRange = nBound;
      Bitmask thisTab = getMask(pWC->pMaskSet, iCur);
      for(pTerm=pWC->a, k=pWC->nTerm; nRow>2 && k; k--, pTerm++){
        if( pTerm->wtFlags & TERM_VIRTUAL ) continue;
        if( (pTerm->prereqAll & notReady)!=thisTab ) continue;
        if( pTerm->eOperator & (WO_EQ|WO_IN|WO_ISNULL) ){
          if( nSkipEq ){
            /* Ignore the first nEq equality matches since the index
            ** has already accounted for these */
            nSkipEq--;
          }else{
            /* Assume each additional equality match reduces the result
            ** set size by a factor of 10 */
            nRow /= 10;
          }
        }else if( pTerm->eOperator & (WO_LT|WO_LE|WO_GT|WO_GE) ){
          if( nSkipRange ){
            /* Ignore the first nBound range constraints since the index
            ** has already accounted for these */
            nSkipRange--;
          }else{
            /* Assume each additional range constraint reduces the result
            ** set size by a factor of 3 */
            nRow /= 3;
          }
        }else{
          /* Any other expression lowers the output row count by half */
          nRow /= 2;
        }
      }
      if( nRow<2 ) nRow = 2;
    }


    WHERETRACE((
      "%s(%s): nEq=%d nInMul=%d estBound=%d bSort=%d bLookup=%d wsFlags=0x%x\n"
      "         notReady=0x%llx nRow=%.2f cost=%.2f used=0x%llx\n",
      pSrc->pTab->zName, (pIdx ? pIdx->zName : "ipk"), 
      nEq, nInMul, estBound, bSort, bLookup, wsFlags,
      notReady, nRow, cost, used
    ));

    /* If this index is the best we have seen so far, then record this
    ** index and its cost in the pCost structure.
    */
    if( (!pIdx || wsFlags)
     && (cost<pCost->rCost || (cost<=pCost->rCost && nRow<pCost->nRow))
    ){
      pCost->rCost = cost;
      pCost->nRow = nRow;
      pCost->used = used;
      pCost->plan.wsFlags = (wsFlags&wsFlagMask);
      pCost->plan.nEq = nEq;
      pCost->plan.u.pIdx = pIdx;
    }

  assert( pCost->plan.u.pIdx==0 || (pCost->plan.wsFlags&WHERE_ROWID_EQ)==0 );
  assert( pSrc->pIndex==0 
       || pCost->plan.u.pIdx==0 
       || pCost->plan.u.pIdx==pSrc->pIndex 
  );

  WHERETRACE(("best index is: %s\n", 
    ((pCost->plan.wsFlags & WHERE_NOT_FULLSCAN)==0 ? "none" : 
         pCost->plan.u.pIdx ? pCost->plan.u.pIdx->zName : "ipk")
  ));
  
  bestOrClauseIndex(pParse, pWC, pSrc, notReady, pOrderBy, pCost);
  bestAutomaticIndex(pParse, pWC, pSrc, notReady, pCost);
  pCost->plan.wsFlags |= eqTermMask;
}

    Bitmask m;                  /* Bitmask value for j or bestJ */
    int isOptimal;              /* Iterator for optimal/non-optimal search */

    memset(&bestPlan, 0, sizeof(bestPlan));
    bestPlan.rCost = SQLITE_BIG_DBL;

    /* Loop through the remaining entries in the FROM clause to find the
    ** next nested loop. The loop tests all FROM clause entries
    ** either once or twice. 
    **
    ** The first test is always performed if there are two or more entries
    ** remaining and never performed if there is only one FROM clause entry
    ** to choose from.  The first test looks for an "optimal" scan.  In
    ** this context an optimal scan is one that uses the same strategy
    ** for the given FROM clause entry as would be selected if the entry
    ** were used as the innermost nested loop.  In other words, a table
    ** is chosen such that the cost of running that table cannot be reduced
    ** by waiting for other tables to run first.  This "optimal" test works
    ** by first assuming that the FROM clause is on the inner loop and finding
    ** its query plan, then checking to see if that query plan uses any
    ** other FROM clause terms that are notReady.  If no notReady terms are
    ** used then the "optimal" query plan works.
    **
    ** The second loop iteration is only performed if no optimal scan
    ** strategies were found by the first loop. This 2nd iteration is used to
    ** search for the lowest cost scan overall.
    **
    ** Previous versions of SQLite performed only the second iteration -
    ** the next outermost loop was always that with the lowest overall
    ** cost. However, this meant that SQLite could select the wrong plan
    ** for scripts such as the following:
    **   
    **   CREATE TABLE t1(a, b); 
    **   CREATE TABLE t2(c, d);
    **   SELECT * FROM t2, t1 WHERE t2.rowid = t1.a;
    **
    ** The best strategy is to iterate through table t1 first. However it
    ** is not possible to determine this with a simple greedy algorithm.
    ** However, since the cost of a linear scan through table t2 is the same 
    ** as the cost of a linear scan through table t1, a simple greedy 
    ** algorithm may choose to use t2 for the outer loop, which is a much
    ** costlier approach.
    */
    for(isOptimal=(iFrom<nTabList-1); isOptimal>=0; isOptimal--){
      Bitmask mask;  /* Mask of tables not yet ready */

      for(j=iFrom, pTabItem=&pTabList->a[j]; j<nTabList; j++, pTabItem++){
        int doNotReorder;    /* True if this table should not be reordered */
        WhereCost sCost;     /* Cost information from best[Virtual]Index() */
        ExprList *pOrderBy;  /* ORDER BY clause for index to optimize */
  
        doNotReorder =  (pTabItem->jointype & (JT_LEFT|JT_CROSS))!=0;
        if( j!=iFrom && doNotReorder ) break;
        m = getMask(pMaskSet, pTabItem->iCursor);
        if( (m & notReady)==0 ){
          if( j==iFrom ) iFrom++;
          continue;
        }
        mask = (isOptimal ? m : notReady);
        pOrderBy = ((i==0 && ppOrderBy )?*ppOrderBy:0);
  
        assert( pTabItem->pTab );
#ifndef SQLITE_OMIT_VIRTUALTABLE
        if( IsVirtual(pTabItem->pTab) ){
          sqlite3_index_info **pp = &pWInfo->a[j].pIdxInfo;
          bestVirtualIndex(pParse, pWC, pTabItem, mask, pOrderBy, &sCost, pp);
        }else 
#endif
        {
          bestBtreeIndex(pParse, pWC, pTabItem, mask, pOrderBy, &sCost);
        }
        assert( isOptimal || (sCost.used&notReady)==0 );

        if( (sCost.used&notReady)==0
         && (bestJ<0 || sCost.rCost<bestPlan.rCost
             || (sCost.rCost<=bestPlan.rCost && sCost.nRow<bestPlan.nRow))
        ){
          WHERETRACE(("... best so far with cost=%g and nRow=%g\n",
                      sCost.rCost, sCost.nRow));
          bestPlan = sCost;
          bestJ = j;
        }
        if( doNotReorder ) break;
      }
    }
    assert( bestJ>=0 );

    INSERT INTO bb VALUES(4);
    SELECT * FROM aa, bb WHERE max(a,b)>2;
  }
} {1 4 3 2 3 4}
do_test select2-4.2 {
  execsql {
    INSERT INTO bb VALUES(0);
    SELECT * FROM aa CROSS JOIN bb WHERE b;
  }
} {1 2 1 4 3 2 3 4}
do_test select2-4.3 {
  execsql {
    SELECT * FROM aa CROSS JOIN bb WHERE NOT b;
  }
} {1 0 3 0}
do_test select2-4.4 {
  execsql {
    SELECT * FROM aa, bb WHERE min(a,b);
  }
} {1 2 1 4 3 2 3 4}

        UNION SELECT y FROM t1 WHERE x BETWEEN 3 and 5;
     SELECT * FROM v4 ORDER BY 1;
  }
} {1 10 2 3 4 5 6 7 8 9 five four three}
do_test triggerA-1.6 {
  db eval {
     CREATE VIEW v5 AS SELECT x, b FROM t1, t2 WHERE y=c;
     SELECT * FROM v5 ORDER BY x DESC;
  }
} {10 1003 9 904 8 805 7 705 6 603 5 504 4 404 3 305 2 203 1 103}

# Create INSTEAD OF triggers on the views.  Run UPDATE and DELETE statements
# using those triggers.  Verify correct operation.
#
do_test triggerA-2.1 {

} {tC {} tA * tB * tD *}
do_test where3-2.5 {
  queryplan {
    SELECT * FROM tA, tB, tC LEFT JOIN tD ON dpk=cx
     WHERE cpk=ax AND bpk=cx
  }
} {tA {} tC * tB * tD *}
do_test where3-2.6 {
  queryplan {
    SELECT * FROM tA, tB, tC LEFT JOIN tD ON dpk=cx
     WHERE bpk=cx AND apk=bx
  }
} {tC {} tB * tA * tD *}
do_test where3-2.7 {
  queryplan {
    SELECT * FROM tA, tB, tC LEFT JOIN tD ON dpk=cx
     WHERE cpk=bx AND apk=cx
  }
} {tB {} tC * tA * tD *}

} {2 4 5 scan 0 sort 0}
do_test where7-1.9 {
  count_steps {
    SELECT a FROM t1 WHERE (b=3 OR c>=10 OR c=4)
  }
} {2 4 5 scan 0 sort 0}
do_test where7-1.10 {

  count_steps {
    SELECT a FROM t1 WHERE (b=3 OR c>=10 OR c=4 OR b>10)
  }
} {2 4 5 scan 0 sort 0}

do_test where7-1.11 {
  count_steps {
    SELECT a FROM t1 WHERE (d=5 AND b=3) OR c==100 ORDER BY a;
  }
} {2 5 scan 0 sort 1}
do_test where7-1.12 {
  count_steps {
    SELECT a FROM t1 WHERE (b BETWEEN 2 AND 4) OR c=100 ORDER BY a
  }
} {1 2 3 5 scan 0 sort 1}
do_test where7-1.13 {






  count_steps {
    SELECT a FROM t1 WHERE (b BETWEEN 0 AND 2) OR (c BETWEEN 9 AND 999)
    ORDER BY +a DESC
  }
} {5 4 1 scan 0 sort 1}

do_test where7-1.14 {

} {IV V 9 0}

do_test where8-3.15 {
  execsql_status {
    SELECT c FROM t1, t2 WHERE a BETWEEN 1 AND 2 OR a = (
      SELECT sum(e IS NULL) FROM t2 AS inner WHERE t2.d>inner.d
    )
    ORDER BY c
  }

} {I I I I I I I I I I II II II II II II II II II II III III III III III 9 1}

#-----------------------------------------------------------------------
# The following tests - where8-4.* - verify that adding or removing 
# indexes does not change the results returned by various queries.
#
do_test where8-4.1 {
  execsql {