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Improve usage of effective_cache_size parameter by assuming that all the

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tables in the query compete for cache space, not just the one we are
currently costing an indexscan for.  This seems more realistic, and it
definitely will help in examples recently exhibited by Stefan
Kaltenbrunner.  To get the total size of all the tables involved, we must
tweak the handling of 'append relations' a bit --- formerly we looked up
information about the child tables on-the-fly during set_append_rel_pathlist,
but it needs to be done before we start doing any cost estimation, so
push it into the add_base_rels_to_query scan.
This commit is contained in:
Tom Lane
2006-09-19 22:49:53 +00:00
parent 45e11d098f
commit b74c543685
11 changed files with 171 additions and 44 deletions
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5
src/backend/utils/adt/selfuncs.c
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@ -15,7 +15,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.211 2006/07/26 17:17:28 momjian Exp $
* $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.212 2006/09/19 22:49:53 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -4647,7 +4647,8 @@ genericcostestimate(PlannerInfo *root,
/* use Mackert and Lohman formula to adjust for cache effects */
pages_fetched = index_pages_fetched(pages_fetched,
index->pages,
index->rel->pages);
(double) index->pages,
root);
/*
* Now compute the total disk access cost, and then report a