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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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109
src/backend/optimizer/util/relnode.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/util/relnode.c,v 1.68 2005/06/06 04:13:36 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/util/relnode.c,v 1.69 2005/06/08 23:02:05 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -21,8 +21,15 @@
#include "optimizer/restrictinfo.h"
#include "optimizer/tlist.h"
#include "parser/parsetree.h"
#include "utils/hsearch.h"
typedef struct JoinHashEntry
{
Relids join_relids; /* hash key --- MUST BE FIRST */
RelOptInfo *join_rel;
} JoinHashEntry;
static RelOptInfo *make_reloptinfo(PlannerInfo *root, int relid,
RelOptKind reloptkind);
static void build_joinrel_tlist(PlannerInfo *root, RelOptInfo *joinrel,
@ -197,6 +204,47 @@ find_base_rel(PlannerInfo *root, int relid)
return NULL; /* keep compiler quiet */
}
/*
* build_join_rel_hash
* Construct the auxiliary hash table for join relations.
*/
static void
build_join_rel_hash(PlannerInfo *root)
{
HTAB *hashtab;
HASHCTL hash_ctl;
ListCell *l;
/* Create the hash table */
MemSet(&hash_ctl, 0, sizeof(hash_ctl));
hash_ctl.keysize = sizeof(Relids);
hash_ctl.entrysize = sizeof(JoinHashEntry);
hash_ctl.hash = bitmap_hash;
hash_ctl.match = bitmap_match;
hash_ctl.hcxt = CurrentMemoryContext;
hashtab = hash_create("JoinRelHashTable",
256L,
&hash_ctl,
HASH_ELEM | HASH_FUNCTION | HASH_COMPARE | HASH_CONTEXT);
/* Insert all the already-existing joinrels */
foreach(l, root->join_rel_list)
{
RelOptInfo *rel = (RelOptInfo *) lfirst(l);
JoinHashEntry *hentry;
bool found;
hentry = (JoinHashEntry *) hash_search(hashtab,
&(rel->relids),
HASH_ENTER,
&found);
Assert(!found);
hentry->join_rel = rel;
}
root->join_rel_hash = hashtab;
}
/*
* find_join_rel
* Returns relation entry corresponding to 'relids' (a set of RT indexes),
@ -205,14 +253,44 @@ find_base_rel(PlannerInfo *root, int relid)
RelOptInfo *
find_join_rel(PlannerInfo *root, Relids relids)
{
ListCell *l;
/*
* Switch to using hash lookup when list grows "too long". The threshold
* is arbitrary and is known only here.
*/
if (!root->join_rel_hash && list_length(root->join_rel_list) > 32)
build_join_rel_hash(root);
foreach(l, root->join_rel_list)
/*
* Use either hashtable lookup or linear search, as appropriate.
*
* Note: the seemingly redundant hashkey variable is used to avoid
* taking the address of relids; unless the compiler is exceedingly
* smart, doing so would force relids out of a register and thus
* probably slow down the list-search case.
*/
if (root->join_rel_hash)
{
RelOptInfo *rel = (RelOptInfo *) lfirst(l);
Relids hashkey = relids;
JoinHashEntry *hentry;
if (bms_equal(rel->relids, relids))
return rel;
hentry = (JoinHashEntry *) hash_search(root->join_rel_hash,
&hashkey,
HASH_FIND,
NULL);
if (hentry)
return hentry->join_rel;
}
else
{
ListCell *l;
foreach(l, root->join_rel_list)
{
RelOptInfo *rel = (RelOptInfo *) lfirst(l);
if (bms_equal(rel->relids, relids))
return rel;
}
}
return NULL;
@ -329,9 +407,24 @@ build_join_rel(PlannerInfo *root,
jointype, restrictlist);
/*
* Add the joinrel to the query's joinrel list.
* Add the joinrel to the query's joinrel list, and store it into
* the auxiliary hashtable if there is one. NB: GEQO requires us
* to append the new joinrel to the end of the list!
*/
root->join_rel_list = lcons(joinrel, root->join_rel_list);
root->join_rel_list = lappend(root->join_rel_list, joinrel);
if (root->join_rel_hash)
{
JoinHashEntry *hentry;
bool found;
hentry = (JoinHashEntry *) hash_search(root->join_rel_hash,
&(joinrel->relids),
HASH_ENTER,
&found);
Assert(!found);
hentry->join_rel = joinrel;
}
return joinrel;
}