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Add the reverse_unordered_selects pragma. (CVS 6314)

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FossilOrigin-Name: bc078e0007b6c3dc07722820bb53798b643212b3
This commit is contained in:
drh
2009-02-23 16:52:07 +00:00
parent 7c5c3cab89
commit 699b3d4f89
6 changed files with 116 additions and 16 deletions
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24
src/where.c
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@@ -16,7 +16,7 @@
** so is applicable. Because this module is responsible for selecting
** indices, you might also think of this module as the "query optimizer".
**
** $Id: where.c,v 1.370 2009/02/20 10:58:42 danielk1977 Exp $
** $Id: where.c,v 1.371 2009/02/23 16:52:08 drh Exp $
*/
#include "sqliteInt.h"
@@ -1837,7 +1837,15 @@ static void bestIndex(
cost += cost*estLog(cost);
WHERETRACE(("... sorting increases cost to %.9g\n", cost));
}
}else if( pParse->db->flags & SQLITE_ReverseOrder ){
/* For application testing, randomly reverse the output order for
** SELECT statements that omit the ORDER BY clause. This will help
** to find cases where
*/
wsFlags |= WHERE_REVERSE;
}
/* Remember this case if it is the best so far */
if( cost<pCost->rCost ){
pCost->rCost = cost;
pCost->nRow = nRow;
@@ -1987,6 +1995,12 @@ static void bestIndex(
cost += cost*estLog(cost);
WHERETRACE(("...... orderby increases cost to %.9g\n", cost));
}
}else if( pParse->db->flags & SQLITE_ReverseOrder ){
/* For application testing, randomly reverse the output order for
** SELECT statements that omit the ORDER BY clause. This will help
** to find cases where
*/
wsFlags |= WHERE_REVERSE;
}
/* Check to see if we can get away with using just the index without
@@ -2747,11 +2761,13 @@ static Bitmask codeOneLoopStart(
/* Case 5: There is no usable index. We must do a complete
** scan of the entire table.
*/
static const u8 aStep[] = { OP_Next, OP_Prev };
static const u8 aStart[] = { OP_Rewind, OP_Last };
assert( bRev==0 || bRev==1 );
assert( omitTable==0 );
assert( bRev==0 );
pLevel->op = OP_Next;
pLevel->op = aStep[bRev];
pLevel->p1 = iCur;
pLevel->p2 = 1 + sqlite3VdbeAddOp2(v, OP_Rewind, iCur, addrBrk);
pLevel->p2 = 1 + sqlite3VdbeAddOp2(v, aStart[bRev], iCur, addrBrk);
pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
codeRowSetEarly = 0;
}