From 04103e00f1f0ce12c29954d069e1d4437467f700 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sat, 29 Jan 2000 19:51:59 +0000
Subject: [PATCH] Modify uses of RelationFlushRelation and
RelationCacheInvalidate so that we *always* rebuild, rather than deleting, an
invalidated relcache entry that has positive refcount. Otherwise an SI cache
overrun leads to dangling Relation pointers all over the place!
---
src/backend/utils/cache/inval.c | 9 +++++----
src/backend/utils/cache/relcache.c | 27 ++++++++++++++++++++++-----
2 files changed, 27 insertions(+), 9 deletions(-)
diff --git a/src/backend/utils/cache/inval.c b/src/backend/utils/cache/inval.c
index ce4230da4f1..473978bd410 100644
--- a/src/backend/utils/cache/inval.c
+++ b/src/backend/utils/cache/inval.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/utils/cache/inval.c,v 1.32 2000/01/26 05:57:17 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/backend/utils/cache/inval.c,v 1.33 2000/01/29 19:51:59 tgl Exp $
*
* Note - this code is real crufty...
*
@@ -548,15 +548,16 @@ CacheIdInvalidate(Index cacheId,
/* --------------------------------
* ResetSystemCaches
*
- * this blows away all tuples in the system catalog caches and
- * all the cached relation descriptors (and closes the files too).
+ * This blows away all tuples in the system catalog caches and
+ * all the cached relation descriptors (and closes their files too).
+ * Relation descriptors that have positive refcounts are then rebuilt.
* --------------------------------
*/
static void
ResetSystemCaches()
{
ResetSystemCache();
- RelationCacheInvalidate(false);
+ RelationCacheInvalidate(true);
}
/* --------------------------------
diff --git a/src/backend/utils/cache/relcache.c b/src/backend/utils/cache/relcache.c
index ea11b026884..4a6c86d84d9 100644
--- a/src/backend/utils/cache/relcache.c
+++ b/src/backend/utils/cache/relcache.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/utils/cache/relcache.c,v 1.87 2000/01/26 05:57:17 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/backend/utils/cache/relcache.c,v 1.88 2000/01/29 19:51:59 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -1406,7 +1406,18 @@ RelationIdInvalidateRelationCacheByRelationId(Oid relationId)
*/
if (PointerIsValid(relation) && !relation->rd_myxactonly)
{
-
+#if 1
+ /*
+ * Seems safest just to NEVER flush rels with positive refcounts.
+ * I think the code only had that proviso as a rather lame method of
+ * cleaning up unused relcache entries that had dangling refcounts
+ * (following elog(ERROR) with an open rel). Now we rely on
+ * RelationCacheAbort to clean up dangling refcounts, so there's no
+ * good reason to ever risk flushing a rel with positive refcount.
+ * IMHO anyway --- tgl 1/29/00.
+ */
+ RelationFlushRelation(&relation, true);
+#else
/*
* The boolean onlyFlushReferenceCountZero in RelationFlushReln()
* should be set to true when we are incrementing the command
@@ -1414,6 +1425,7 @@ RelationIdInvalidateRelationCacheByRelationId(Oid relationId)
* can be determined by checking the current xaction status.
*/
RelationFlushRelation(&relation, CurrentXactInProgress());
+#endif
}
}
@@ -1436,7 +1448,7 @@ RelationFlushIndexes(Relation *r,
if (relation->rd_rel->relkind == RELKIND_INDEX && /* XXX style */
(!OidIsValid(accessMethodId) ||
relation->rd_rel->relam == accessMethodId))
- RelationFlushRelation(&relation, false);
+ RelationFlushRelation(&relation, true);
}
#endif
@@ -1469,9 +1481,14 @@ RelationIdInvalidateRelationCacheByAccessMethodId(Oid accessMethodId)
* Will blow away either all the cached relation descriptors or
* those that have a zero reference count.
*
+ * CAUTION: this is only called with onlyFlushReferenceCountZero=true
+ * at present, so that relation descriptors with positive refcounts
+ * are rebuilt rather than clobbered. It would only be safe to use a
+ * "false" parameter in a totally idle backend with no open relations.
+ *
* This is currently used only to recover from SI message buffer overflow,
- * so onlyFlushReferenceCountZero is always false. We do not blow away
- * transaction-local relations, since they cannot be targets of SI updates.
+ * so we do not blow away transaction-local relations; they cannot be
+ * targets of SI updates.
*/
void
RelationCacheInvalidate(bool onlyFlushReferenceCountZero)
--
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