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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 20:30:52 +00:00
parent 0fa322a14e
commit aaaacf0f6c
1 changed files with 31 additions and 27 deletions
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56
src/backend/optimizer/path/joinpath.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/joinpath.c,v 1.71.2.1 2005/01/23 02:24:16 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/joinpath.c,v 1.71.2.2 2005/10/25 20:30:52 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -901,6 +901,7 @@ select_mergejoin_clauses(RelOptInfo *joinrel,
{
List *result_list = NIL;
bool isouterjoin = IS_OUTER_JOIN(jointype);
bool have_nonmergeable_joinclause = false;
List *i;
foreach(i, restrictlist)
@ -913,36 +914,15 @@ 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.
*/
if (isouterjoin)
{
if (restrictinfo->ispusheddown)
if (isouterjoin && restrictinfo->ispusheddown)
continue;
switch (jointype)
{
case JOIN_RIGHT:
if (restrictinfo->mergejoinoperator == InvalidOid)
return NIL; /* not mergejoinable */
break;
case JOIN_FULL:
if (restrictinfo->mergejoinoperator == InvalidOid)
elog(ERROR, "FULL JOIN is only supported with mergejoinable join conditions");
break;
default:
/* otherwise, it's OK to have nonmergeable join quals */
break;
}
}
if (restrictinfo->mergejoinoperator == InvalidOid)
{
have_nonmergeable_joinclause = true;
continue; /* not mergejoinable */
}
clause = restrictinfo->clause;
/* these must be OK, since check_mergejoinable accepted the clause */
@ -954,6 +934,30 @@ select_mergejoin_clauses(RelOptInfo *joinrel,
(VARISRELMEMBER(left->varno, innerrel) &&
VARISRELMEMBER(right->varno, outerrel)))
result_list = lcons(restrictinfo, result_list);
else
have_nonmergeable_joinclause = true;
}
/*
* 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:
elog(ERROR, "FULL JOIN is only supported with mergejoinable join conditions");
break;
default:
/* otherwise, it's OK to have nonmergeable join quals */
break;
}
}
return result_list;