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Adjust the definition of is_pushed_down so that it's always true for INNER

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JOIN quals, just like WHERE quals, even if they reference every one of the
join's relations.  Now that we can reorder outer and inner joins, it's
possible 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 for
the node.  (If it were, the join could produce null-extended rows that it
shouldn't.)  Per bug report from Pelle Johansson.
REL8_3_STABLE
Tom Lane 19 years ago
parent e472f13f99
commit 8249409bc1
2 changed files with 50 additions and 45 deletions
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
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  1. 79
      src/backend/optimizer/plan/initsplan.c
  2. 16
      src/include/nodes/relation.h

79
src/backend/optimizer/plan/initsplan.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/plan/initsplan.c,v 1.130 2007/02/13 02:31:03 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/plan/initsplan.c,v 1.131 2007/02/16 20:57:19 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -43,7 +43,6 @@ static OuterJoinInfo *make_outerjoininfo(PlannerInfo *root,
Relids left_rels, Relids right_rels,
bool is_full_join, Node *clause);
static void distribute_qual_to_rels(PlannerInfo *root, Node *clause,
bool is_pushed_down,
bool is_deduced,
bool below_outer_join,
Relids qualscope,
@ -283,12 +282,11 @@ deconstruct_recurse(PlannerInfo *root, Node *jtnode, bool below_outer_join,
}
/*
* Now process the top-level quals. These are always marked as
* "pushed down", since they clearly didn't come from a JOIN expr.
* Now process the top-level quals.
*/
foreach(l, (List *) f->quals)
distribute_qual_to_rels(root, (Node *) lfirst(l),
true, false, below_outer_join,
false, below_outer_join,
*qualscope, NULL, NULL);
}
else if (IsA(jtnode, JoinExpr))
@ -389,7 +387,7 @@ deconstruct_recurse(PlannerInfo *root, Node *jtnode, bool below_outer_join,
/* Process the qual clauses */
foreach(qual, (List *) j->quals)
distribute_qual_to_rels(root, (Node *) lfirst(qual),
false, false, below_outer_join,
false, below_outer_join,
*qualscope, ojscope, nonnullable_rels);
/* Now we can add the OuterJoinInfo to oj_info_list */
@ -600,8 +598,6 @@ make_outerjoininfo(PlannerInfo *root,
* EquivalenceClasses.
*
* 'clause': the qual clause to be distributed
* 'is_pushed_down': if TRUE, force the clause to be marked 'is_pushed_down'
* (this indicates the clause came from a FromExpr, not a JoinExpr)
* 'is_deduced': TRUE if the qual came from implied-equality deduction
* 'below_outer_join': TRUE if the qual is from a JOIN/ON that is below the
* nullable side of a higher-level outer join
@ -619,7 +615,6 @@ make_outerjoininfo(PlannerInfo *root,
*/
static void
distribute_qual_to_rels(PlannerInfo *root, Node *clause,
bool is_pushed_down,
bool is_deduced,
bool below_outer_join,
Relids qualscope,
@ -627,6 +622,7 @@ distribute_qual_to_rels(PlannerInfo *root, Node *clause,
Relids outerjoin_nonnullable)
{
Relids relids;
bool is_pushed_down;
bool outerjoin_delayed;
bool pseudoconstant = false;
bool maybe_equivalence;
@ -692,17 +688,37 @@ distribute_qual_to_rels(PlannerInfo *root, Node *clause,
root->hasPseudoConstantQuals = true;
/* if not below outer join, push it to top of tree */
if (!below_outer_join)
{
relids = get_relids_in_jointree((Node *) root->parse->jointree);
is_pushed_down = true;
}
}
}
}
/*
/*----------
* Check to see if clause application must be delayed by outer-join
* considerations.
*
* A word about is_pushed_down: we mark the qual as "pushed down" if
* it is (potentially) applicable at a level different from its original
* syntactic level. This flag is used to distinguish OUTER JOIN ON quals
* from other quals pushed down to the same joinrel. The rules are:
* WHERE quals and INNER JOIN quals: is_pushed_down = true.
* Non-degenerate OUTER JOIN quals: is_pushed_down = false.
* Degenerate OUTER JOIN quals: is_pushed_down = true.
* A "degenerate" OUTER JOIN qual is one that doesn't mention the
* non-nullable side, and hence can be pushed down into the nullable side
* without changing the join result. It is correct to treat it as a
* regular filter condition at the level where it is evaluated.
*
* Note: it is not immediately obvious that a simple boolean is enough
* for this: if for some reason we were to attach a degenerate qual to
* its original join level, it would need to be treated as an outer join
* qual there. However, this cannot happen, because all the rels the
* clause mentions must be in the outer join's min_righthand, therefore
* the join it needs must be formed before the outer join; and we always
* attach quals to the lowest level where they can be evaluated. But
* if we were ever to re-introduce a mechanism for delaying evaluation
* of "expensive" quals, this area would need work.
*----------
*/
if (is_deduced)
{
@ -713,6 +729,7 @@ distribute_qual_to_rels(PlannerInfo *root, Node *clause,
* where the qual belongs.
*/
Assert(!ojscope);
is_pushed_down = true;
outerjoin_delayed = false;
/* Don't feed it back for more deductions */
maybe_equivalence = false;
@ -722,12 +739,7 @@ distribute_qual_to_rels(PlannerInfo *root, Node *clause,
{
/*
* The qual is attached to an outer join and mentions (some of the)
* rels on the nonnullable side.
*
* Note: an outer-join qual that mentions only nullable-side rels can
* be pushed down into the nullable side without changing the join
* result, so we treat it almost the same as an ordinary inner-join
* qual (see below).
* 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 gone
@ -751,12 +763,19 @@ distribute_qual_to_rels(PlannerInfo *root, Node *clause,
*/
Assert(ojscope);
relids = ojscope;
is_pushed_down = false;
outerjoin_delayed = true;
Assert(!pseudoconstant);
}
else
{
/* Normal qual clause; check to see if must be delayed by outer join */
/*
* Normal qual clause or degenerate outer-join clause. Either way,
* we can mark it as pushed-down.
*/
is_pushed_down = true;
/* Check to see if must be delayed by outer join */
outerjoin_delayed = check_outerjoin_delay(root, &relids);
if (outerjoin_delayed)
@ -791,17 +810,6 @@ distribute_qual_to_rels(PlannerInfo *root, Node *clause,
maybe_outer_join = false;
}
/*
* Mark the qual as "pushed down" if it can be applied at a level below
* its original syntactic level. This allows us to distinguish original
* JOIN/ON quals from higher-level quals pushed down to the same joinrel.
* A qual originating from WHERE is always considered "pushed down". Note
* that for an outer-join qual, we have to compare to ojscope not
* qualscope.
*/
if (!is_pushed_down)
is_pushed_down = !bms_equal(relids, ojscope ? ojscope : qualscope);
/*
* Build the RestrictInfo node itself.
*/
@ -915,7 +923,7 @@ distribute_qual_to_rels(PlannerInfo *root, Node *clause,
* If so, add relids to *relids_p to reflect the lowest safe level for
* evaluating the qual, and return TRUE.
*
* For a non-outer-join qual, we can evaluate the qual as soon as (1) we have
* For an is_pushed_down qual, we can evaluate the qual as soon as (1) we have
* all the rels it mentions, and (2) we are at or above any outer joins that
* can null any of these rels and are below the syntactic location of the
* 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,
* B/C join is done first then the join to A can null C, so a qual actually
* mentioning only C cannot be applied below the join to A.
*
* For an outer-join qual, this isn't going to determine where we place the
* For a non-pushed-down qual, this isn't going to determine where we place the
* qual, but we need to determine outerjoin_delayed anyway so we can decide
* whether the qual is potentially useful for equivalence deductions.
*/
@ -1101,12 +1109,9 @@ process_implied_equality(PlannerInfo *root,
/*
* Push the new clause into all the appropriate restrictinfo lists.
*
* Note: we mark the qual "pushed down" to ensure that it can never be
* taken for an original JOIN/ON clause.
*/
distribute_qual_to_rels(root, (Node *) clause,
true, true, below_outer_join,
true, below_outer_join,
qualscope, NULL, NULL);
}

16
src/include/nodes/relation.h
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@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.134 2007/01/22 20:00:40 tgl Exp $
* $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.135 2007/02/16 20:57:19 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -797,14 +797,14 @@ typedef struct HashPath
* join, we prevent it from being evaluated below the outer join's joinrel.
* When we do form the outer join's joinrel, we still need to distinguish
* those quals that are actually in that join's JOIN/ON condition from those
* that appeared higher in the tree and were pushed down to the join rel
* that appeared elsewhere in the tree and were pushed down to the join rel
* because they used no other rels. That's what the is_pushed_down flag is
* for; it tells us that a qual came from a point above the join of the
* set of base rels listed in required_relids. A clause that originally came
* from WHERE will *always* have its is_pushed_down flag set; a clause that
* came from an INNER JOIN condition, but doesn't use all the rels being
* joined, will also have is_pushed_down set because it will get attached to
* some lower joinrel.
* for; it tells us that a qual is not an OUTER JOIN qual for the set of base
* rels listed in required_relids. A clause that originally came from WHERE
* or an INNER JOIN condition will *always* have its is_pushed_down flag set.
* It's possible for an OUTER JOIN clause to be marked is_pushed_down too,
* if we decide that it can be pushed down into the nullable side of the join.
* In that case it acts as a plain filter qual for wherever it gets evaluated.
*
* When application of a qual must be delayed by outer join, we also mark it
* with outerjoin_delayed = true. This isn't redundant with required_relids

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