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Overview
Comment:Improved handling of constants and especially constant functions in the ORDER BY clause of a query. Do not optimize out "ORDER BY random()". Fix for ticket [65bdeb9739605cc2296].
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SHA1: dca1945aeb3fb005263f9be00ee8e72b966ae303
User & Date: drh 2014-02-26 02:26:09
Context
2014-02-26
13:53
In the command-line shell for CSV import, if the lines are \r\n terminated and the last field is blank, make sure an empty string and not a "\r" string is imported. check-in: 9c2e7612 user: drh tags: trunk
02:26
Improved handling of constants and especially constant functions in the ORDER BY clause of a query. Do not optimize out "ORDER BY random()". Fix for ticket [65bdeb9739605cc2296]. check-in: dca1945a user: drh tags: trunk
2014-02-25
21:55
Do not allow temporary registers to be in use across an OP_Yield within a co-routine. Fix for ticket [8c63ff0eca81a9132d8]. check-in: 97a8c973 user: drh tags: trunk
Changes
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Changes to src/where.c.

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    } /* end-if not one-row */

    /* Mark off any other ORDER BY terms that reference pLoop */
    if( isOrderDistinct ){
      orderDistinctMask |= pLoop->maskSelf;
      for(i=0; i<nOrderBy; i++){
        Expr *p;

        if( MASKBIT(i) & obSat ) continue;
        p = pOrderBy->a[i].pExpr;
        if( (exprTableUsage(&pWInfo->sMaskSet, p)&~orderDistinctMask)==0 ){


          obSat |= MASKBIT(i);
        }
      }
    }
  } /* End the loop over all WhereLoops from outer-most down to inner-most */
  if( obSat==obDone ) return 1;
  if( !isOrderDistinct ) return 0;
................................................................................
  ** and work forward so that the added virtual terms are never processed.
  */
  exprAnalyzeAll(pTabList, &pWInfo->sWC);
  if( db->mallocFailed ){
    goto whereBeginError;
  }

  /* If the ORDER BY (or GROUP BY) clause contains references to general
  ** expressions, then we won't be able to satisfy it using indices, so
  ** go ahead and disable it now.
  */
  if( pOrderBy && (wctrlFlags & WHERE_WANT_DISTINCT)!=0 ){
    for(ii=0; ii<pOrderBy->nExpr; ii++){
      Expr *pExpr = sqlite3ExprSkipCollate(pOrderBy->a[ii].pExpr);
      if( pExpr->op!=TK_COLUMN ){
        pWInfo->pOrderBy = pOrderBy = 0;
        break;
      }else if( pExpr->iColumn<0 ){
        break;
      }
    }
  }

  if( wctrlFlags & WHERE_WANT_DISTINCT ){
    if( isDistinctRedundant(pParse, pTabList, &pWInfo->sWC, pResultSet) ){
      /* The DISTINCT marking is pointless.  Ignore it. */
      pWInfo->eDistinct = WHERE_DISTINCT_UNIQUE;
    }else if( pOrderBy==0 ){
      /* Try to ORDER BY the result set to make distinct processing easier */
      pWInfo->wctrlFlags |= WHERE_DISTINCTBY;







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    } /* end-if not one-row */

    /* Mark off any other ORDER BY terms that reference pLoop */
    if( isOrderDistinct ){
      orderDistinctMask |= pLoop->maskSelf;
      for(i=0; i<nOrderBy; i++){
        Expr *p;
        Bitmask mTerm;
        if( MASKBIT(i) & obSat ) continue;
        p = pOrderBy->a[i].pExpr;
        mTerm = exprTableUsage(&pWInfo->sMaskSet,p);
        if( mTerm==0 && !sqlite3ExprIsConstant(p) ) continue;
        if( (mTerm&~orderDistinctMask)==0 ){
          obSat |= MASKBIT(i);
        }
      }
    }
  } /* End the loop over all WhereLoops from outer-most down to inner-most */
  if( obSat==obDone ) return 1;
  if( !isOrderDistinct ) return 0;
................................................................................
  ** and work forward so that the added virtual terms are never processed.
  */
  exprAnalyzeAll(pTabList, &pWInfo->sWC);
  if( db->mallocFailed ){
    goto whereBeginError;
  }

















  if( wctrlFlags & WHERE_WANT_DISTINCT ){
    if( isDistinctRedundant(pParse, pTabList, &pWInfo->sWC, pResultSet) ){
      /* The DISTINCT marking is pointless.  Ignore it. */
      pWInfo->eDistinct = WHERE_DISTINCT_UNIQUE;
    }else if( pOrderBy==0 ){
      /* Try to ORDER BY the result set to make distinct processing easier */
      pWInfo->wctrlFlags |= WHERE_DISTINCTBY;

Changes to test/where2.test.

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  }
} {85 6 7396 7402 sort t1 i1xy}
do_test where2-2.3 {
  queryplan {
    SELECT * FROM t1 WHERE rowid=85 AND x=6 AND y=7396 ORDER BY random();
  }
} {85 6 7396 7402 nosort t1 *}






































# Efficient handling of forward and reverse table scans.
#
do_test where2-3.1 {
  queryplan {
    SELECT * FROM t1 ORDER BY rowid LIMIT 2







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  }
} {85 6 7396 7402 sort t1 i1xy}
do_test where2-2.3 {
  queryplan {
    SELECT * FROM t1 WHERE rowid=85 AND x=6 AND y=7396 ORDER BY random();
  }
} {85 6 7396 7402 nosort t1 *}

# Ticket [65bdeb9739605cc22966f49208452996ff29a640] 2014-02-26
# Make sure "ORDER BY random" does not gets optimized out.
#
do_test where2-2.4 {
  db eval {
    CREATE TABLE x1(a INTEGER PRIMARY KEY, b DEFAULT 1);
    WITH RECURSIVE
       cnt(x) AS (VALUES(1) UNION ALL SELECT x+1 FROM cnt WHERE x<50)
    INSERT INTO x1 SELECT x, 1 FROM cnt;
    CREATE TABLE x2(x INTEGER PRIMARY KEY);
    INSERT INTO x2 VALUES(1);
  }
  set sql {SELECT * FROM x1, x2 WHERE x=1 ORDER BY random()}
  set out1 [db eval $sql]
  set out2 [db eval $sql]
  set out3 [db eval $sql]
  expr {$out1!=$out2 && $out2!=$out3}
} {1}
do_execsql_test where2-2.5 {
  -- random() is not optimized out
  EXPLAIN SELECT * FROM x1, x2 WHERE x=1 ORDER BY random();
} {/ random/}
do_execsql_test where2-2.5b {
  -- random() is not optimized out
  EXPLAIN SELECT * FROM x1, x2 WHERE x=1 ORDER BY random();
} {/ SorterOpen /}
do_execsql_test where2-2.6 {
  -- other constant functions are optimized out
  EXPLAIN SELECT * FROM x1, x2 WHERE x=1 ORDER BY abs(5);
} {~/ abs/}
do_execsql_test where2-2.6b {
  -- other constant functions are optimized out
  EXPLAIN SELECT * FROM x1, x2 WHERE x=1 ORDER BY abs(5);
} {~/ SorterOpen /}



# Efficient handling of forward and reverse table scans.
#
do_test where2-3.1 {
  queryplan {
    SELECT * FROM t1 ORDER BY rowid LIMIT 2