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Fix longstanding bug that would sometimes let the planner generate a bad plan

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for an outer join; symptom is bogus error "RIGHT JOIN is only supported with
merge-joinable join conditions".  Problem was that select_mergejoin_clauses
did its tests in the wrong order.  We need to force left join not right join
for a merge join when there are non-mergeable join clauses; but the test for
this only accounted for mergejoinability of the clause operator, and not
whether the left and right Vars were of the proper relations.  Per report
from Jean-Pierre Pelletier.
This commit is contained in:
Tom Lane 2005-10-25 20:30:30 +00:00
parent 62cfa0f75c
commit ddb4015ec0
1 changed files with 37 additions and 32 deletions
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69
src/backend/optimizer/path/joinpath.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/joinpath.c,v 1.96 2005/10/15 02:49:20 momjian Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/joinpath.c,v 1.97 2005/10/25 20:30:30 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -795,6 +795,7 @@ select_mergejoin_clauses(RelOptInfo *joinrel,
{
List *result_list = NIL;
bool isouterjoin = IS_OUTER_JOIN(jointype);
bool have_nonmergeable_joinclause = false;
ListCell *l;
foreach(l, restrictlist)
@ -803,42 +804,19 @@ select_mergejoin_clauses(RelOptInfo *joinrel,
/*
* If processing an outer join, only use its own join clauses in the
* merge. For inner joins we need not be so picky.
*
* Furthermore, if it is a right/full join then *all* the explicit join
* clauses must be mergejoinable, else the executor will fail. If we
* are asked for a right join then just return NIL to indicate no
* mergejoin is possible (we can handle it as a left join instead). If
* we are asked for a full join then emit an error, because there is
* no fallback.
* merge. For inner joins we can use pushed-down clauses too.
* (Note: we don't set have_nonmergeable_joinclause here because
* pushed-down clauses will become otherquals not joinquals.)
*/
if (isouterjoin)
{
if (restrictinfo->is_pushed_down)
continue;
switch (jointype)
{
case JOIN_RIGHT:
if (!restrictinfo->can_join ||
restrictinfo->mergejoinoperator == InvalidOid)
return NIL; /* not mergejoinable */
break;
case JOIN_FULL:
if (!restrictinfo->can_join ||
restrictinfo->mergejoinoperator == InvalidOid)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("FULL JOIN is only supported with merge-joinable join conditions")));
break;
default:
/* otherwise, it's OK to have nonmergeable join quals */
break;
}
}
if (isouterjoin && restrictinfo->is_pushed_down)
continue;
if (!restrictinfo->can_join ||
restrictinfo->mergejoinoperator == InvalidOid)
{
have_nonmergeable_joinclause = true;
continue; /* not mergejoinable */
}
/*
* Check if clause is usable with these input rels. All the vars
@ -856,10 +834,37 @@ select_mergejoin_clauses(RelOptInfo *joinrel,
/* lefthand side is inner */
}
else
{
have_nonmergeable_joinclause = true;
continue; /* no good for these input relations */
}
result_list = lcons(restrictinfo, result_list);
}
/*
* If it is a right/full join then *all* the explicit join clauses must be
* mergejoinable, else the executor will fail. If we are asked for a right
* join then just return NIL to indicate no mergejoin is possible (we can
* handle it as a left join instead). If we are asked for a full join then
* emit an error, because there is no fallback.
*/
if (have_nonmergeable_joinclause)
{
switch (jointype)
{
case JOIN_RIGHT:
return NIL; /* not mergejoinable */
case JOIN_FULL:
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("FULL JOIN is only supported with merge-joinable join conditions")));
break;
default:
/* otherwise, it's OK to have nonmergeable join quals */
break;
}
}
return result_list;
}