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Teach planner about some cases where a restriction clause can be

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propagated inside an outer join.  In particular, given
LEFT JOIN ON (A = B) WHERE A = constant, we cannot conclude that
B = constant at the top level (B might be null instead), but we
can nonetheless put a restriction B = constant into the quals for
B's relation, since no inner-side rows not meeting that condition
can contribute to the final result.  Similarly, given
FULL JOIN USING (J) WHERE J = constant, we can't directly conclude
that either input J variable = constant, but it's OK to push such
quals into each input rel.  Per recent gripe from Kim Bisgaard.
Along the way, remove 'valid_everywhere' flag from RestrictInfo,
as on closer analysis it was not being used for anything, and was
defined backwards anyway.
This commit is contained in:
Tom Lane
2005-07-02 23:00:42 +00:00
parent ea1e2b948d
commit cc5e80b8d1
13 changed files with 424 additions and 114 deletions
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18
src/include/nodes/relation.h
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@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.115 2005/06/13 23:14:49 tgl Exp $
* $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.116 2005/07/02 23:00:42 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -87,6 +87,15 @@ typedef struct PlannerInfo
List *equi_key_list; /* list of lists of equijoined
* PathKeyItems */
List *left_join_clauses; /* list of RestrictInfos for outer join
* clauses w/nonnullable var on left */
List *right_join_clauses; /* list of RestrictInfos for outer join
* clauses w/nonnullable var on right */
List *full_join_clauses; /* list of RestrictInfos for full outer
* join clauses */
List *in_info_list; /* list of InClauseInfos */
List *query_pathkeys; /* desired pathkeys for query_planner(),
@@ -95,6 +104,7 @@ typedef struct PlannerInfo
double tuple_fraction; /* tuple_fraction passed to query_planner */
bool hasJoinRTEs; /* true if any RTEs are RTE_JOIN kind */
bool hasOuterJoins; /* true if any RTEs are outer joins */
bool hasHavingQual; /* true if havingQual was non-null */
} PlannerInfo;
@@ -695,10 +705,6 @@ typedef struct HashPath
* joined, will also have is_pushed_down set because it will get attached to
* some lower joinrel.
*
* We also store a valid_everywhere flag, which says that the clause is not
* affected by any lower-level outer join, and therefore any conditions it
* asserts can be presumed true throughout the plan tree.
*
* In general, the referenced clause might be arbitrarily complex. The
* kinds of clauses we can handle as indexscan quals, mergejoin clauses,
* or hashjoin clauses are fairly limited --- the code for each kind of
@@ -725,8 +731,6 @@ typedef struct RestrictInfo
bool is_pushed_down; /* TRUE if clause was pushed down in level */
bool valid_everywhere; /* TRUE if valid on every level */
/*
* This flag is set true if the clause looks potentially useful as a
* merge or hash join clause, that is if it is a binary opclause with