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Marginal hack to avoid spending a lot of time in find_join_rel during

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large planning problems: when the list of join rels gets too long, make
an auxiliary hash table that hashes on the identifying Bitmapset.
This commit is contained in:
Tom Lane
2005-06-08 23:02:05 +00:00
parent 77c168a836
commit e3a33a9a9f
9 changed files with 194 additions and 25 deletions
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30
src/backend/optimizer/geqo/geqo_eval.c
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@@ -6,7 +6,7 @@
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/backend/optimizer/geqo/geqo_eval.c,v 1.74 2005/06/05 22:32:55 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/geqo/geqo_eval.c,v 1.75 2005/06/08 23:02:04 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -47,7 +47,8 @@ geqo_eval(Gene *tour, int num_gene, GeqoEvalData *evaldata)
MemoryContext oldcxt;
RelOptInfo *joinrel;
Cost fitness;
List *savelist;
int savelength;
struct HTAB *savehash;
/*
* Because gimme_tree considers both left- and right-sided trees,
@@ -83,13 +84,19 @@ geqo_eval(Gene *tour, int num_gene, GeqoEvalData *evaldata)
* gimme_tree will add entries to root->join_rel_list, which may or may
* not already contain some entries. The newly added entries will be
* recycled by the MemoryContextDelete below, so we must ensure that
* the list is restored to its former state before exiting. With the
* new List implementation, the easiest way is to make a duplicate list
* that gimme_tree can modify.
* the list is restored to its former state before exiting. We can
* do this by truncating the list to its original length. NOTE this
* assumes that any added entries are appended at the end!
*
* We also must take care not to mess up the outer join_rel_hash,
* if there is one. We can do this by just temporarily setting the
* link to NULL. (If we are dealing with enough join rels, which we
* very likely are, a new hash table will get built and used locally.)
*/
savelist = evaldata->root->join_rel_list;
savelength = list_length(evaldata->root->join_rel_list);
savehash = evaldata->root->join_rel_hash;
evaldata->root->join_rel_list = list_copy(savelist);
evaldata->root->join_rel_hash = NULL;
/* construct the best path for the given combination of relations */
joinrel = gimme_tree(tour, num_gene, evaldata);
@@ -105,8 +112,13 @@ geqo_eval(Gene *tour, int num_gene, GeqoEvalData *evaldata)
else
fitness = DBL_MAX;
/* restore join_rel_list */
evaldata->root->join_rel_list = savelist;
/*
* Restore join_rel_list to its former state, and put back original
* hashtable if any.
*/
evaldata->root->join_rel_list = list_truncate(evaldata->root->join_rel_list,
savelength);
evaldata->root->join_rel_hash = savehash;
/* release all the memory acquired within gimme_tree */
MemoryContextSwitchTo(oldcxt);