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Commit8249409

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Adjust the definition of is_pushed_down so that it's always true for INNER
JOIN quals, just like WHERE quals, even if they reference every one of thejoin's relations. Now that we can reorder outer and inner joins, it'spossible for such a qual to end up being assigned to an outer join plan node,and we mustn't have it treated as a join qual rather than a filter qual forthe node. (If it were, the join could produce null-extended rows that itshouldn't.) Per bug report from Pelle Johansson.
1 parente472f13 commit8249409

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2 files changed

+50
-45
lines changed

2 files changed

+50
-45
lines changed

‎src/backend/optimizer/plan/initsplan.c‎

Lines changed: 42 additions & 37 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/optimizer/plan/initsplan.c,v 1.130 2007/02/13 02:31:03 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/optimizer/plan/initsplan.c,v 1.131 2007/02/16 20:57:19 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -43,7 +43,6 @@ static OuterJoinInfo *make_outerjoininfo(PlannerInfo *root,
4343
Relidsleft_rels,Relidsright_rels,
4444
boolis_full_join,Node*clause);
4545
staticvoiddistribute_qual_to_rels(PlannerInfo*root,Node*clause,
46-
boolis_pushed_down,
4746
boolis_deduced,
4847
boolbelow_outer_join,
4948
Relidsqualscope,
@@ -283,12 +282,11 @@ deconstruct_recurse(PlannerInfo *root, Node *jtnode, bool below_outer_join,
283282
}
284283

285284
/*
286-
* Now process the top-level quals. These are always marked as
287-
* "pushed down", since they clearly didn't come from a JOIN expr.
285+
* Now process the top-level quals.
288286
*/
289287
foreach(l, (List*)f->quals)
290288
distribute_qual_to_rels(root, (Node*)lfirst(l),
291-
true,false,below_outer_join,
289+
false,below_outer_join,
292290
*qualscope,NULL,NULL);
293291
}
294292
elseif (IsA(jtnode,JoinExpr))
@@ -389,7 +387,7 @@ deconstruct_recurse(PlannerInfo *root, Node *jtnode, bool below_outer_join,
389387
/* Process the qual clauses */
390388
foreach(qual, (List*)j->quals)
391389
distribute_qual_to_rels(root, (Node*)lfirst(qual),
392-
false,false,below_outer_join,
390+
false,below_outer_join,
393391
*qualscope,ojscope,nonnullable_rels);
394392

395393
/* Now we can add the OuterJoinInfo to oj_info_list */
@@ -600,8 +598,6 @@ make_outerjoininfo(PlannerInfo *root,
600598
* EquivalenceClasses.
601599
*
602600
* 'clause': the qual clause to be distributed
603-
* 'is_pushed_down': if TRUE, force the clause to be marked 'is_pushed_down'
604-
*(this indicates the clause came from a FromExpr, not a JoinExpr)
605601
* 'is_deduced': TRUE if the qual came from implied-equality deduction
606602
* 'below_outer_join': TRUE if the qual is from a JOIN/ON that is below the
607603
*nullable side of a higher-level outer join
@@ -619,14 +615,14 @@ make_outerjoininfo(PlannerInfo *root,
619615
*/
620616
staticvoid
621617
distribute_qual_to_rels(PlannerInfo*root,Node*clause,
622-
boolis_pushed_down,
623618
boolis_deduced,
624619
boolbelow_outer_join,
625620
Relidsqualscope,
626621
Relidsojscope,
627622
Relidsouterjoin_nonnullable)
628623
{
629624
Relidsrelids;
625+
boolis_pushed_down;
630626
boolouterjoin_delayed;
631627
boolpseudoconstant= false;
632628
boolmaybe_equivalence;
@@ -692,17 +688,37 @@ distribute_qual_to_rels(PlannerInfo *root, Node *clause,
692688
root->hasPseudoConstantQuals= true;
693689
/* if not below outer join, push it to top of tree */
694690
if (!below_outer_join)
695-
{
696691
relids=get_relids_in_jointree((Node*)root->parse->jointree);
697-
is_pushed_down= true;
698-
}
699692
}
700693
}
701694
}
702695

703-
/*
696+
/*----------
704697
* Check to see if clause application must be delayed by outer-join
705698
* considerations.
699+
*
700+
* A word about is_pushed_down: we mark the qual as "pushed down" if
701+
* it is (potentially) applicable at a level different from its original
702+
* syntactic level. This flag is used to distinguish OUTER JOIN ON quals
703+
* from other quals pushed down to the same joinrel. The rules are:
704+
*WHERE quals and INNER JOIN quals: is_pushed_down = true.
705+
*Non-degenerate OUTER JOIN quals: is_pushed_down = false.
706+
*Degenerate OUTER JOIN quals: is_pushed_down = true.
707+
* A "degenerate" OUTER JOIN qual is one that doesn't mention the
708+
* non-nullable side, and hence can be pushed down into the nullable side
709+
* without changing the join result. It is correct to treat it as a
710+
* regular filter condition at the level where it is evaluated.
711+
*
712+
* Note: it is not immediately obvious that a simple boolean is enough
713+
* for this: if for some reason we were to attach a degenerate qual to
714+
* its original join level, it would need to be treated as an outer join
715+
* qual there. However, this cannot happen, because all the rels the
716+
* clause mentions must be in the outer join's min_righthand, therefore
717+
* the join it needs must be formed before the outer join; and we always
718+
* attach quals to the lowest level where they can be evaluated. But
719+
* if we were ever to re-introduce a mechanism for delaying evaluation
720+
* of "expensive" quals, this area would need work.
721+
*----------
706722
*/
707723
if (is_deduced)
708724
{
@@ -713,6 +729,7 @@ distribute_qual_to_rels(PlannerInfo *root, Node *clause,
713729
* where the qual belongs.
714730
*/
715731
Assert(!ojscope);
732+
is_pushed_down= true;
716733
outerjoin_delayed= false;
717734
/* Don't feed it back for more deductions */
718735
maybe_equivalence= false;
@@ -722,12 +739,7 @@ distribute_qual_to_rels(PlannerInfo *root, Node *clause,
722739
{
723740
/*
724741
* The qual is attached to an outer join and mentions (some of the)
725-
* rels on the nonnullable side.
726-
*
727-
* Note: an outer-join qual that mentions only nullable-side rels can
728-
* be pushed down into the nullable side without changing the join
729-
* result, so we treat it almost the same as an ordinary inner-join
730-
* qual (see below).
742+
* rels on the nonnullable side, so it's not degenerate.
731743
*
732744
* We can't use such a clause to deduce equivalence (the left and right
733745
* sides might be unequal above the join because one of them has gone
@@ -751,12 +763,19 @@ distribute_qual_to_rels(PlannerInfo *root, Node *clause,
751763
*/
752764
Assert(ojscope);
753765
relids=ojscope;
766+
is_pushed_down= false;
754767
outerjoin_delayed= true;
755768
Assert(!pseudoconstant);
756769
}
757770
else
758771
{
759-
/* Normal qual clause; check to see if must be delayed by outer join */
772+
/*
773+
* Normal qual clause or degenerate outer-join clause. Either way,
774+
* we can mark it as pushed-down.
775+
*/
776+
is_pushed_down= true;
777+
778+
/* Check to see if must be delayed by outer join */
760779
outerjoin_delayed=check_outerjoin_delay(root,&relids);
761780

762781
if (outerjoin_delayed)
@@ -791,17 +810,6 @@ distribute_qual_to_rels(PlannerInfo *root, Node *clause,
791810
maybe_outer_join= false;
792811
}
793812

794-
/*
795-
* Mark the qual as "pushed down" if it can be applied at a level below
796-
* its original syntactic level. This allows us to distinguish original
797-
* JOIN/ON quals from higher-level quals pushed down to the same joinrel.
798-
* A qual originating from WHERE is always considered "pushed down". Note
799-
* that for an outer-join qual, we have to compare to ojscope not
800-
* qualscope.
801-
*/
802-
if (!is_pushed_down)
803-
is_pushed_down= !bms_equal(relids,ojscope ?ojscope :qualscope);
804-
805813
/*
806814
* Build the RestrictInfo node itself.
807815
*/
@@ -915,7 +923,7 @@ distribute_qual_to_rels(PlannerInfo *root, Node *clause,
915923
* If so, add relids to *relids_p to reflect the lowest safe level for
916924
* evaluating the qual, and return TRUE.
917925
*
918-
* Fora non-outer-join qual, we can evaluate the qual as soon as (1) we have
926+
* Foran is_pushed_down qual, we can evaluate the qual as soon as (1) we have
919927
* all the rels it mentions, and (2) we are at or above any outer joins that
920928
* can null any of these rels and are below the syntactic location of the
921929
* given qual. We must enforce (2) because pushing down such a clause below
@@ -935,7 +943,7 @@ distribute_qual_to_rels(PlannerInfo *root, Node *clause,
935943
* B/C join is done first then the join to A can null C, so a qual actually
936944
* mentioning only C cannot be applied below the join to A.
937945
*
938-
* Foran outer-join qual, this isn't going to determine where we place the
946+
* Fora non-pushed-down qual, this isn't going to determine where we place the
939947
* qual, but we need to determine outerjoin_delayed anyway so we can decide
940948
* whether the qual is potentially useful for equivalence deductions.
941949
*/
@@ -1101,12 +1109,9 @@ process_implied_equality(PlannerInfo *root,
11011109

11021110
/*
11031111
* Push the new clause into all the appropriate restrictinfo lists.
1104-
*
1105-
* Note: we mark the qual "pushed down" to ensure that it can never be
1106-
* taken for an original JOIN/ON clause.
11071112
*/
11081113
distribute_qual_to_rels(root, (Node*)clause,
1109-
true,true,below_outer_join,
1114+
true,below_outer_join,
11101115
qualscope,NULL,NULL);
11111116
}
11121117

‎src/include/nodes/relation.h‎

Lines changed: 8 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.134 2007/01/22 20:00:40 tgl Exp $
10+
* $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.135 2007/02/16 20:57:19 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -797,14 +797,14 @@ typedef struct HashPath
797797
* join, we prevent it from being evaluated below the outer join's joinrel.
798798
* When we do form the outer join's joinrel, we still need to distinguish
799799
* those quals that are actually in that join's JOIN/ON condition from those
800-
* that appearedhigher in the tree and were pushed down to the join rel
800+
* that appearedelsewhere in the tree and were pushed down to the join rel
801801
* because they used no other rels. That's what the is_pushed_down flag is
802-
* for; it tells us that a qualcame from a point abovethejoin ofthe
803-
*set of baserels listed in required_relids.A clause that originally came
804-
*from WHEREwill *always* have its is_pushed_down flag set; a clause that
805-
*came fromanINNER JOINcondition, but doesn't use all the rels being
806-
*joined, will also have is_pushed_down set because it will get attached to
807-
*some lower joinrel.
802+
* for; it tells us that a qualis not an OUTER JOIN qual fortheset ofbase
803+
* rels listed in required_relids.A clause that originally came from WHERE
804+
*or an INNER JOIN conditionwill *always* have its is_pushed_down flag set.
805+
*It's possible foranOUTER JOINclause to be marked is_pushed_down too,
806+
*if we decide that it can be pushed down into the nullable side of the join.
807+
*In that case it acts as a plain filter qual for wherever it gets evaluated.
808808
*
809809
* When application of a qual must be delayed by outer join, we also mark it
810810
* with outerjoin_delayed = true. This isn't redundant with required_relids

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