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Avoid scanning the relcache during AtEOSubXact_RelationCache when there

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is nothing to do, which is most of the time.  This is another simple
improvement to cut subtransaction entry/exit overhead.
This commit is contained in:
Tom Lane 2004-11-20 20:19:52 +00:00
parent 8ecbc46bdb
commit 3e3f283e31
1 changed files with 30 additions and 1 deletions

31
src/backend/utils/cache/relcache.c vendored

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/cache/relcache.c,v 1.211 2004/09/16 16:58:35 tgl Exp $
* $PostgreSQL: pgsql/src/backend/utils/cache/relcache.c,v 1.212 2004/11/20 20:19:52 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -120,6 +120,11 @@ static long relcacheInvalsReceived = 0L;
*/
static List *initFileRelationIds = NIL;
/*
* This flag lets us optimize away work in AtEOSubXact_RelationCache().
*/
static bool need_eosubxact_work = false;
/*
* RelationBuildDescInfo exists so code can be shared
* between RelationIdGetRelation() and RelationSysNameGetRelation()
@ -2087,6 +2092,9 @@ AtEOXact_RelationCache(bool isCommit)
relation->rd_indexvalid = 0;
}
}
/* Once done with the transaction, we can reset need_eosubxact_work */
need_eosubxact_work = false;
}
/*
@ -2103,6 +2111,21 @@ AtEOSubXact_RelationCache(bool isCommit, SubTransactionId mySubid,
HASH_SEQ_STATUS status;
RelIdCacheEnt *idhentry;
/*
* In the majority of subtransactions there is not anything for this
* routine to do, and since there are usually many entries in the
* relcache, uselessly scanning the cache represents a surprisingly
* large fraction of the subtransaction entry/exit overhead. To avoid
* this, we keep a static flag that must be set whenever a condition
* is created that requires subtransaction-end work. (Currently, this
* means either a relation is created in the current xact, or an index
* list is forced.) For simplicity, the flag remains set till end of
* top-level transaction, even though we could clear it earlier in some
* cases.
*/
if (!need_eosubxact_work)
return;
hash_seq_init(&status, RelationIdCache);
while ((idhentry = (RelIdCacheEnt *) hash_seq_search(&status)) != NULL)
@ -2184,6 +2207,9 @@ RelationBuildLocalRelation(const char *relname,
/* it's being created in this transaction */
rel->rd_createSubid = GetCurrentSubTransactionId();
/* must flag that we have rels created in this transaction */
need_eosubxact_work = true;
/* is it a temporary relation? */
rel->rd_istemp = isTempNamespace(relnamespace);
@ -2745,6 +2771,8 @@ RelationSetIndexList(Relation relation, List *indexIds)
list_free(relation->rd_indexlist);
relation->rd_indexlist = indexIds;
relation->rd_indexvalid = 2; /* mark list as forced */
/* must flag that we have a forced index list */
need_eosubxact_work = true;
}
/*
@ -3172,6 +3200,7 @@ load_relcache_init_file(void)
rel->rd_refcnt = 0;
rel->rd_indexvalid = 0;
rel->rd_indexlist = NIL;
rel->rd_createSubid = InvalidSubTransactionId;
MemSet(&rel->pgstat_info, 0, sizeof(rel->pgstat_info));
/*