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Fix join-removal logic for pseudoconstant and outerjoin-delayed quals.

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In these cases a qual can get marked with the removable rel in its
required_relids, but this is just to schedule its evaluation correctly, not
because it really depends on the rel.  We were assuming that, in effect,
we could throw away *all* quals so marked, which is nonsense.  Tighten up
the logic to be a little more paranoid about which quals belong to the
outer join being considered for removal, and arrange for all quals that
don't belong to be updated so they will still get evaluated correctly.

Also fix another problem that happened to be exposed by this test case,
which was that make_join_rel() was failing to notice some cases where
a constant-false qual could be used to prove a join relation empty.  If it's
a pushed-down constant false, then the relation is empty even if it's an
outer join, because the qual applies after the outer join expansion.

Per report from Nathan Grange.  Back-patch into 9.0.
This commit is contained in:
Tom Lane
2010-09-14 23:15:29 +00:00
parent 3522217b63
commit 4e97631e6a
6 changed files with 187 additions and 31 deletions
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40
src/backend/optimizer/path/joinrels.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/joinrels.c,v 1.105 2010/02/26 02:00:45 momjian Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/joinrels.c,v 1.106 2010/09/14 23:15:29 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -29,7 +29,8 @@ static bool has_join_restriction(PlannerInfo *root, RelOptInfo *rel);
static bool has_legal_joinclause(PlannerInfo *root, RelOptInfo *rel);
static bool is_dummy_rel(RelOptInfo *rel);
static void mark_dummy_rel(RelOptInfo *rel);
static bool restriction_is_constant_false(List *restrictlist);
static bool restriction_is_constant_false(List *restrictlist,
bool only_pushed_down);
/*
@ -603,7 +604,10 @@ make_join_rel(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2)
*
* Also, a provably constant-false join restriction typically means that
* we can skip evaluating one or both sides of the join. We do this by
* marking the appropriate rel as dummy.
* marking the appropriate rel as dummy. For outer joins, a constant-false
* restriction that is pushed down still means the whole join is dummy,
* while a non-pushed-down one means that no inner rows will join so we
* can treat the inner rel as dummy.
*
* We need only consider the jointypes that appear in join_info_list, plus
* JOIN_INNER.
@ -612,7 +616,7 @@ make_join_rel(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2)
{
case JOIN_INNER:
if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
restriction_is_constant_false(restrictlist))
restriction_is_constant_false(restrictlist, false))
{
mark_dummy_rel(joinrel);
break;
@ -625,12 +629,13 @@ make_join_rel(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2)
restrictlist);
break;
case JOIN_LEFT:
if (is_dummy_rel(rel1))
if (is_dummy_rel(rel1) ||
restriction_is_constant_false(restrictlist, true))
{
mark_dummy_rel(joinrel);
break;
}
if (restriction_is_constant_false(restrictlist) &&
if (restriction_is_constant_false(restrictlist, false) &&
bms_is_subset(rel2->relids, sjinfo->syn_righthand))
mark_dummy_rel(rel2);
add_paths_to_joinrel(root, joinrel, rel1, rel2,
@ -641,7 +646,8 @@ make_join_rel(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2)
restrictlist);
break;
case JOIN_FULL:
if (is_dummy_rel(rel1) && is_dummy_rel(rel2))
if ((is_dummy_rel(rel1) && is_dummy_rel(rel2)) ||
restriction_is_constant_false(restrictlist, true))
{
mark_dummy_rel(joinrel);
break;
@ -665,7 +671,7 @@ make_join_rel(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2)
bms_is_subset(sjinfo->min_righthand, rel2->relids))
{
if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
restriction_is_constant_false(restrictlist))
restriction_is_constant_false(restrictlist, false))
{
mark_dummy_rel(joinrel);
break;
@ -687,6 +693,12 @@ make_join_rel(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2)
create_unique_path(root, rel2, rel2->cheapest_total_path,
sjinfo) != NULL)
{
if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
restriction_is_constant_false(restrictlist, false))
{
mark_dummy_rel(joinrel);
break;
}
add_paths_to_joinrel(root, joinrel, rel1, rel2,
JOIN_UNIQUE_INNER, sjinfo,
restrictlist);
@ -696,12 +708,13 @@ make_join_rel(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2)
}
break;
case JOIN_ANTI:
if (is_dummy_rel(rel1))
if (is_dummy_rel(rel1) ||
restriction_is_constant_false(restrictlist, true))
{
mark_dummy_rel(joinrel);
break;
}
if (restriction_is_constant_false(restrictlist) &&
if (restriction_is_constant_false(restrictlist, false) &&
bms_is_subset(rel2->relids, sjinfo->syn_righthand))
mark_dummy_rel(rel2);
add_paths_to_joinrel(root, joinrel, rel1, rel2,
@ -947,9 +960,11 @@ mark_dummy_rel(RelOptInfo *rel)
* join situations this will leave us computing cartesian products only to
* decide there's no match for an outer row, which is pretty stupid. So,
* we need to detect the case.
*
* If only_pushed_down is TRUE, then consider only pushed-down quals.
*/
static bool
restriction_is_constant_false(List *restrictlist)
restriction_is_constant_false(List *restrictlist, bool only_pushed_down)
{
ListCell *lc;
@ -964,6 +979,9 @@ restriction_is_constant_false(List *restrictlist)
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
Assert(IsA(rinfo, RestrictInfo));
if (only_pushed_down && !rinfo->is_pushed_down)
continue;
if (rinfo->clause && IsA(rinfo->clause, Const))
{
Const *con = (Const *) rinfo->clause;