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Deduce equality constraints that are implied by transitivity of

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mergejoinable qual clauses, and add them to the query quals.  For
example, WHERE a = b AND b = c will cause us to add AND a = c.
This is necessary to ensure that it's safe to use these variables
as interchangeable sort keys, which is something 7.0 knows how to do.
Should provide a useful improvement in planning ability, too.
This commit is contained in:
Tom Lane
2000-07-24 03:11:01 +00:00
parent c39c198bc3
commit cd9f0ca545
6 changed files with 398 additions and 158 deletions
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3
src/include/optimizer/paths.h
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@@ -8,7 +8,7 @@
* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: paths.h,v 1.45 2000/05/31 00:28:38 petere Exp $
* $Id: paths.h,v 1.46 2000/07/24 03:10:54 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -90,6 +90,7 @@ typedef enum
} PathKeysComparison;
extern void add_equijoined_keys(Query *root, RestrictInfo *restrictinfo);
extern void generate_implied_equalities(Query *root);
extern List *canonicalize_pathkeys(Query *root, List *pathkeys);
extern PathKeysComparison compare_pathkeys(List *keys1, List *keys2);
extern bool pathkeys_contained_in(List *keys1, List *keys2);