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Planner speedup hacking. Avoid saving useless pathkeys, so that path

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comparison does not consider paths different when they differ only in
uninteresting aspects of sort order.  (We had a special case of this
consideration for indexscans already, but generalize it to apply to
ordered join paths too.)  Be stricter about what is a canonical pathkey
to allow faster pathkey comparison.  Cache canonical pathkeys and
dispersion stats for left and right sides of a RestrictInfo's clause,
to avoid repeated computation.  Total speedup will depend on number of
tables in a query, but I see about 4x speedup of planning phase for
a sample seven-table query.
This commit is contained in:
Tom Lane
2000-12-14 22:30:45 +00:00
parent db11f4382a
commit ea166f1146
16 changed files with 622 additions and 365 deletions
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10
src/include/nodes/relation.h
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@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: relation.h,v 1.51 2000/12/12 23:33:32 tgl Exp $
* $Id: relation.h,v 1.52 2000/12/14 22:30:44 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -504,8 +504,16 @@ typedef struct RestrictInfo
Oid left_sortop; /* leftside sortop needed for mergejoin */
Oid right_sortop; /* rightside sortop needed for mergejoin */
/* cache space for mergeclause processing; NIL if not yet set */
List *left_pathkey; /* canonical pathkey for left side */
List *right_pathkey; /* canonical pathkey for right side */
/* valid if clause is hashjoinable, else InvalidOid: */
Oid hashjoinoperator; /* copy of clause operator */
/* cache space for hashclause processing; -1 if not yet set */
Selectivity left_dispersion; /* dispersion of left side */
Selectivity right_dispersion; /* dispersion of right side */
} RestrictInfo;
/*