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Switch the planner over to treating qualifications of a JOIN_SEMI join as

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though it is an inner rather than outer join type.  This essentially means
that we don't bother to separate "pushed down" qual conditions from actual
join quals at a semijoin plan node; which is okay because the restrictions of
SQL syntax make it impossible to have a pushed-down qual that references the
inner side of a semijoin.  This allows noticeably better optimization of
IN/EXISTS cases than we had before, since the equivalence-class machinery can
now use those quals.  Also fix a couple of other mistakes that had essentially
disabled the ability to unique-ify the inner relation and then join it to just
a subset of the left-hand relations.  An example case using the regression
database is

select * from tenk1 a, tenk1 b
where (a.unique1,b.unique2) in (select unique1,unique2 from tenk1 c);

which is planned reasonably well by 8.3 and earlier but had been forcing a
cartesian join of a/b in CVS HEAD.
This commit is contained in:
Tom Lane 2008-11-22 22:47:06 +00:00
parent 86422cbbfc
commit 8309d006cb
6 changed files with 87 additions and 34 deletions
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4
src/backend/optimizer/path/costsize.c
View File

@ -54,7 +54,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.200 2008/10/21 20:42:52 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.201 2008/11/22 22:47:05 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -2481,7 +2481,7 @@ set_joinrel_size_estimates(PlannerInfo *root, RelOptInfo *rel,
break;
case JOIN_SEMI:
nrows = outer_rel->rows * jselec;
nrows *= pselec;
/* pselec not used */
break;
case JOIN_ANTI:
nrows = outer_rel->rows * (1.0 - jselec);

4
src/backend/optimizer/path/indxpath.c
View File

@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/indxpath.c,v 1.233 2008/09/12 14:56:13 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/indxpath.c,v 1.234 2008/11/22 22:47:05 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -1647,10 +1647,10 @@ best_inner_indexscan(PlannerInfo *root, RelOptInfo *rel,
switch (jointype)
{
case JOIN_INNER:
case JOIN_SEMI:
isouterjoin = false;
break;
case JOIN_LEFT:
case JOIN_SEMI:
case JOIN_ANTI:
isouterjoin = true;
break;

4
src/backend/optimizer/path/joinpath.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/joinpath.c,v 1.118 2008/10/04 21:56:53 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/joinpath.c,v 1.119 2008/11/22 22:47:06 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -744,12 +744,12 @@ hash_inner_and_outer(PlannerInfo *root,
switch (jointype)
{
case JOIN_INNER:
case JOIN_SEMI:
case JOIN_UNIQUE_OUTER:
case JOIN_UNIQUE_INNER:
isouterjoin = false;
break;
case JOIN_LEFT:
case JOIN_SEMI:
case JOIN_ANTI:
isouterjoin = true;
break;

57
src/backend/optimizer/path/joinrels.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/joinrels.c,v 1.94 2008/08/17 19:40:11 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/joinrels.c,v 1.95 2008/11/22 22:47:06 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -419,6 +419,27 @@ join_is_legal(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2,
match_sjinfo = sjinfo;
reversed = true;
}
else if (sjinfo->jointype == JOIN_SEMI &&
bms_equal(sjinfo->syn_righthand, rel2->relids))
{
/*
* For a semijoin, we can join the RHS to anything else by
* unique-ifying the RHS.
*/
if (match_sjinfo)
return false; /* invalid join path */
match_sjinfo = sjinfo;
reversed = false;
}
else if (sjinfo->jointype == JOIN_SEMI &&
bms_equal(sjinfo->syn_righthand, rel1->relids))
{
/* Reversed semijoin case */
if (match_sjinfo)
return false; /* invalid join path */
match_sjinfo = sjinfo;
reversed = true;
}
else
{
/*----------
@ -444,14 +465,24 @@ join_is_legal(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2,
* We assume that make_outerjoininfo() set things up correctly
* so that we'll only match to some SJ if the join is valid.
* Set flag here to check at bottom of loop.
*
* For a semijoin, assume it's okay if either side fully contains
* the RHS (per the unique-ification case above).
*----------
*/
if (bms_overlap(rel1->relids, sjinfo->min_righthand) &&
if (sjinfo->jointype != JOIN_SEMI &&
bms_overlap(rel1->relids, sjinfo->min_righthand) &&
bms_overlap(rel2->relids, sjinfo->min_righthand))
{
/* seems OK */
Assert(!bms_overlap(joinrelids, sjinfo->min_lefthand));
}
else if (sjinfo->jointype == JOIN_SEMI &&
(bms_is_subset(sjinfo->syn_righthand, rel1->relids) ||
bms_is_subset(sjinfo->syn_righthand, rel2->relids)))
{
/* seems OK */
}
else
is_valid_inner = false;
}
@ -612,15 +643,23 @@ make_join_rel(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2)
restrictlist);
break;
case JOIN_SEMI:
if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
restriction_is_constant_false(restrictlist))
/*
* Do these steps only if we actually have a regular semijoin,
* as opposed to a case where we should unique-ify the RHS.
*/
if (bms_is_subset(sjinfo->min_lefthand, rel1->relids) &&
bms_is_subset(sjinfo->min_righthand, rel2->relids))
{
mark_dummy_rel(joinrel);
break;
if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
restriction_is_constant_false(restrictlist))
{
mark_dummy_rel(joinrel);
break;
}
add_paths_to_joinrel(root, joinrel, rel1, rel2,
JOIN_SEMI, sjinfo,
restrictlist);
}
add_paths_to_joinrel(root, joinrel, rel1, rel2,
JOIN_SEMI, sjinfo,
restrictlist);
/*
* If we know how to unique-ify the RHS and one input rel is

28
src/backend/optimizer/plan/initsplan.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/plan/initsplan.c,v 1.144 2008/10/25 19:51:32 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/plan/initsplan.c,v 1.145 2008/11/22 22:47:06 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -851,16 +851,11 @@ distribute_qual_to_rels(PlannerInfo *root, Node *clause,
maybe_equivalence = false;
maybe_outer_join = false;
}
else if (bms_overlap(relids, outerjoin_nonnullable) &&
(jointype != JOIN_SEMI ||
bms_nonempty_difference(relids, outerjoin_nonnullable)))
else if (bms_overlap(relids, outerjoin_nonnullable))
{
/*
* The qual is attached to an outer join and mentions (some of the)
* rels on the nonnullable side, so it's not degenerate. (For a
* JOIN_SEMI qual, we consider it non-degenerate only if it mentions
* both sides of the join --- if it mentions only one side, it can
* be pushed down.)
* rels on the nonnullable side, so it's not degenerate.
*
* We can't use such a clause to deduce equivalence (the left and
* right sides might be unequal above the join because one of them has
@ -1062,6 +1057,7 @@ distribute_sublink_quals_to_rels(PlannerInfo *root,
SpecialJoinInfo *sjinfo;
Relids qualscope;
Relids ojscope;
Relids outerjoin_nonnullable;
ListCell *l;
/*
@ -1076,17 +1072,27 @@ distribute_sublink_quals_to_rels(PlannerInfo *root,
fslink->jointype,
quals);
/* Treat as inner join if SEMI, outer join if ANTI */
qualscope = bms_union(sjinfo->syn_lefthand, sjinfo->syn_righthand);
ojscope = bms_union(sjinfo->min_lefthand, sjinfo->min_righthand);
if (fslink->jointype == JOIN_SEMI)
{
ojscope = outerjoin_nonnullable = NULL;
}
else
{
Assert(fslink->jointype == JOIN_ANTI);
ojscope = bms_union(sjinfo->min_lefthand, sjinfo->min_righthand);
outerjoin_nonnullable = fslink->lefthand;
}
/* Distribute the join quals much as for a regular LEFT JOIN */
/* Distribute the join quals much as for a regular JOIN node */
foreach(l, quals)
{
Node *qual = (Node *) lfirst(l);
distribute_qual_to_rels(root, qual,
false, below_outer_join, fslink->jointype,
qualscope, ojscope, fslink->lefthand);
qualscope, ojscope, outerjoin_nonnullable);
}
/* Now we can add the SpecialJoinInfo to join_info_list */

24
src/include/nodes/nodes.h
View File

@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/nodes/nodes.h,v 1.214 2008/10/21 20:42:53 tgl Exp $
* $PostgreSQL: pgsql/src/include/nodes/nodes.h,v 1.215 2008/11/22 22:47:06 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -542,15 +542,23 @@ typedef enum JoinType
/*
* OUTER joins are those for which pushed-down quals must behave differently
* from the join's own quals. This is in fact everything except INNER joins.
* However, this macro must also exclude the JOIN_UNIQUE symbols since those
* are temporary proxies for what will eventually be an INNER join.
* from the join's own quals. This is in fact everything except INNER and
* SEMI joins. However, this macro must also exclude the JOIN_UNIQUE symbols
* since those are temporary proxies for what will eventually be an INNER
* join.
*
* Note: in some places it is preferable to treat JOIN_SEMI as not being
* an outer join, since it doesn't produce null-extended rows. Be aware
* of that distinction when deciding whether to use this macro.
* Note: semijoins are a hybrid case, but we choose to treat them as not
* being outer joins. This is okay principally because the SQL syntax makes
* it impossible to have a pushed-down qual that refers to the inner relation
* of a semijoin; so there is no strong need to distinguish join quals from
* pushed-down quals. This is convenient because for almost all purposes,
* quals attached to a semijoin can be treated the same as innerjoin quals.
*/
#define IS_OUTER_JOIN(jointype) \
((jointype) > JOIN_INNER && (jointype) < JOIN_UNIQUE_OUTER)
(((1 << (jointype)) & \
((1 << JOIN_LEFT) | \
(1 << JOIN_FULL) | \
(1 << JOIN_RIGHT) | \
(1 << JOIN_ANTI))) != 0)
#endif /* NODES_H */