I wrote:
> I'll get you a real fix as soon as I can, but might not be till
> tomorrow.
The attached patch (against 8.4.x) fixes the problem as far as I can
tell. Please test.
regards, tom lane
Index: src/backend/utils/cache/relcache.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/utils/cache/relcache.c,v
retrieving revision 1.287
diff -c -r1.287 relcache.c
*** src/backend/utils/cache/relcache.c 11 Jun 2009 14:49:05 -0000 1.287
--- src/backend/utils/cache/relcache.c 25 Sep 2009 17:32:02 -0000
***************
*** 1386,1392 ****
*
* The data we insert here is pretty incomplete/bogus, but it'll serve to
* get us launched. RelationCacheInitializePhase2() will read the real
! * data from pg_class and replace what we've done here.
*/
relation->rd_rel = (Form_pg_class) palloc0(CLASS_TUPLE_SIZE);
--- 1386,1394 ----
*
* The data we insert here is pretty incomplete/bogus, but it'll serve to
* get us launched. RelationCacheInitializePhase2() will read the real
! * data from pg_class and replace what we've done here. Note in particular
! * that relowner is left as zero; this cues RelationCacheInitializePhase2
! * that the real data isn't there yet.
*/
relation->rd_rel = (Form_pg_class) palloc0(CLASS_TUPLE_SIZE);
***************
*** 2603,2619 ****
* rows and replace the fake entries with them. Also, if any of the
* relcache entries have rules or triggers, load that info the hard way
* since it isn't recorded in the cache file.
*/
hash_seq_init(&status, RelationIdCache);
while ((idhentry = (RelIdCacheEnt *) hash_seq_search(&status)) != NULL)
{
Relation relation = idhentry->reldesc;
/*
* If it's a faked-up entry, read the real pg_class tuple.
*/
! if (needNewCacheFile && relation->rd_isnailed)
{
HeapTuple htup;
Form_pg_class relp;
--- 2605,2635 ----
* rows and replace the fake entries with them. Also, if any of the
* relcache entries have rules or triggers, load that info the hard way
* since it isn't recorded in the cache file.
+ *
+ * Whenever we access the catalogs to read data, there is a possibility
+ * of a shared-inval cache flush causing relcache entries to be removed.
+ * Since hash_seq_search only guarantees to still work after the *current*
+ * entry is removed, it's unsafe to continue the hashtable scan afterward.
+ * We handle this by restarting the scan from scratch after each access.
+ * This is theoretically O(N^2), but the number of entries that actually
+ * need to be fixed is small enough that it doesn't matter.
*/
hash_seq_init(&status, RelationIdCache);
while ((idhentry = (RelIdCacheEnt *) hash_seq_search(&status)) != NULL)
{
Relation relation = idhentry->reldesc;
+ bool restart = false;
+
+ /*
+ * Make sure *this* entry doesn't get flushed while we work with it.
+ */
+ RelationIncrementReferenceCount(relation);
/*
* If it's a faked-up entry, read the real pg_class tuple.
*/
! if (relation->rd_rel->relowner == InvalidOid)
{
HeapTuple htup;
Form_pg_class relp;
***************
*** 2630,2636 ****
* Copy tuple to relation->rd_rel. (See notes in
* AllocateRelationDesc())
*/
- Assert(relation->rd_rel != NULL);
memcpy((char *) relation->rd_rel, (char *) relp, CLASS_TUPLE_SIZE);
/* Update rd_options while we have the tuple */
--- 2646,2651 ----
***************
*** 2639,2660 ****
RelationParseRelOptions(relation, htup);
/*
! * Also update the derived fields in rd_att.
*/
! relation->rd_att->tdtypeid = relp->reltype;
! relation->rd_att->tdtypmod = -1; /* unnecessary, but... */
! relation->rd_att->tdhasoid = relp->relhasoids;
ReleaseSysCache(htup);
}
/*
* Fix data that isn't saved in relcache cache file.
*/
if (relation->rd_rel->relhasrules && relation->rd_rules == NULL)
RelationBuildRuleLock(relation);
if (relation->rd_rel->relhastriggers && relation->trigdesc == NULL)
RelationBuildTriggers(relation);
}
/*
--- 2654,2710 ----
RelationParseRelOptions(relation, htup);
/*
! * Check the values in rd_att were set up correctly. (We cannot
! * just copy them over now: formrdesc must have set up the
! * rd_att data correctly to start with, because it may already
! * have been copied into one or more catcache entries.)
*/
! Assert(relation->rd_att->tdtypeid == relp->reltype);
! Assert(relation->rd_att->tdtypmod == -1);
! Assert(relation->rd_att->tdhasoid == relp->relhasoids);
ReleaseSysCache(htup);
+
+ /* relowner had better be OK now, else we'll loop forever */
+ if (relation->rd_rel->relowner == InvalidOid)
+ elog(ERROR, "invalid relowner in pg_class entry for \"%s\"",
+ RelationGetRelationName(relation));
+
+ restart = true;
}
/*
* Fix data that isn't saved in relcache cache file.
+ *
+ * relhasrules or relhastriggers could possibly be wrong or out of
+ * date. If we don't actually find any rules or triggers, clear the
+ * local copy of the flag so that we don't get into an infinite loop
+ * here. We don't make any attempt to fix the pg_class entry, though.
*/
if (relation->rd_rel->relhasrules && relation->rd_rules == NULL)
+ {
RelationBuildRuleLock(relation);
+ if (relation->rd_rules == NULL)
+ relation->rd_rel->relhasrules = false;
+ restart = true;
+ }
if (relation->rd_rel->relhastriggers && relation->trigdesc == NULL)
+ {
RelationBuildTriggers(relation);
+ if (relation->trigdesc == NULL)
+ relation->rd_rel->relhastriggers = false;
+ restart = true;
+ }
+
+ /* Release hold on the relation */
+ RelationDecrementReferenceCount(relation);
+
+ /* Now, restart the hashtable scan if needed */
+ if (restart)
+ {
+ hash_seq_term(&status);
+ hash_seq_init(&status, RelationIdCache);
+ }
}
/*
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