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Do not flatten subqueries in a join where the subquery includes a LIMIT.

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Ticket #1634.  This is just an initial fix.  Many test cases need to be
added prior to closing the ticket. (CVS 2987)

FossilOrigin-Name: af18c0f431a1a6349e40249009f2ac222f8c8114
This commit is contained in:
drh
2006-01-21 22:19:54 +00:00
parent bcdb66166e
commit ac83963afa
3 changed files with 32 additions and 17 deletions
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35
src/select.c
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@@ -12,7 +12,7 @@
** This file contains C code routines that are called by the parser
** to handle SELECT statements in SQLite.
**
** $Id: select.c,v 1.296 2006/01/20 18:10:57 drh Exp $
** $Id: select.c,v 1.297 2006/01/21 22:19:55 drh Exp $
*/
#include "sqliteInt.h"
@@ -2020,6 +2020,10 @@ static void substSelect(Select *p, int iTable, ExprList *pEList){
** (12) The subquery is not the right term of a LEFT OUTER JOIN or the
** subquery has no WHERE clause. (added by ticket #350)
**
** (13) The subquery and outer query do not both use LIMIT
**
** (14) The subquery does not use OFFSET
**
** In this routine, the "p" parameter is a pointer to the outer query.
** The subquery is p->pSrc->a[iFrom]. isAgg is true if the outer query
** uses aggregates and subqueryIsAgg is true if the subquery uses aggregates.
@@ -2054,18 +2058,26 @@ static int flattenSubquery(
pSubitem = &pSrc->a[iFrom];
pSub = pSubitem->pSelect;
assert( pSub!=0 );
if( isAgg && subqueryIsAgg ) return 0;
if( subqueryIsAgg && pSrc->nSrc>1 ) return 0;
if( isAgg && subqueryIsAgg ) return 0; /* Restriction (1) */
if( subqueryIsAgg && pSrc->nSrc>1 ) return 0; /* Restriction (2) */
pSubSrc = pSub->pSrc;
assert( pSubSrc );
if( (pSub->pLimit && p->pLimit) || pSub->pOffset ||
(pSub->pLimit && isAgg) ) return 0;
if( pSubSrc->nSrc==0 ) return 0;
if( pSub->isDistinct && (pSrc->nSrc>1 || isAgg) ){
return 0;
/* Prior to version 3.1.2, when LIMIT and OFFSET had to be simple constants,
** not arbitrary expresssions, we allowed some combining of LIMIT and OFFSET
** because they could be computed at compile-time. But when LIMIT and OFFSET
** became arbitrary expressions, we were forced to add restrictions (13)
** and (14). */
if( pSub->pLimit && p->pLimit ) return 0; /* Restriction (13) */
if( pSub->pOffset ) return 0; /* Restriction (14) */
if( pSubSrc->nSrc==0 ) return 0; /* Restriction (7) */
if( (pSub->isDistinct || pSub->pLimit)
&& (pSrc->nSrc>1 || isAgg) ){ /* Restrictions (4)(5)(8)(9) */
return 0;
}
if( p->isDistinct && subqueryIsAgg ) return 0; /* Restriction (6) */
if( (p->disallowOrderBy || p->pOrderBy) && pSub->pOrderBy ){
return 0; /* Restriction (11) */
}
if( p->isDistinct && subqueryIsAgg ) return 0;
if( (p->disallowOrderBy || p->pOrderBy) && pSub->pOrderBy ) return 0;
/* Restriction 3: If the subquery is a join, make sure the subquery is
** not used as the right operand of an outer join. Examples of why this
@@ -2195,6 +2207,9 @@ static int flattenSubquery(
/*
** SELECT ... FROM (SELECT ... LIMIT a OFFSET b) LIMIT x OFFSET y;
**
** One is tempted to try to add a and b to combine the limits. But this
** does not work if either limit is negative.
*/
if( pSub->pLimit ){
p->pLimit = pSub->pLimit;