relcache-rebuild.diff

diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
index 5f4ae1291c6..d7037d02a75 100644
--- a/src/backend/replication/logical/reorderbuffer.c
+++ b/src/backend/replication/logical/reorderbuffer.c
@@ -2096,6 +2096,7 @@ ReorderBufferExecuteInvalidations(ReorderBuffer *rb, ReorderBufferTXN *txn)
 
 	for (i = 0; i < txn->ninvalidations; i++)
 		LocalExecuteInvalidationMessage(&txn->invalidations[i]);
+	ProcessPendingRelcacheRebuilds();
 }
 
 /*
diff --git a/src/backend/storage/ipc/sinval.c b/src/backend/storage/ipc/sinval.c
index 563e2906e36..4528a17a9f7 100644
--- a/src/backend/storage/ipc/sinval.c
+++ b/src/backend/storage/ipc/sinval.c
@@ -127,6 +127,8 @@ ReceiveSharedInvalidMessages(
 		 */
 	} while (nummsgs == MAXINVALMSGS);
 
+	ProcessPendingRelcacheRebuilds();
+
 	/*
 	 * We are now caught up.  If we received a catchup signal, reset that
 	 * flag, and call SICleanupQueue().  This is not so much because we need
diff --git a/src/backend/utils/cache/inval.c b/src/backend/utils/cache/inval.c
index 16d86a29390..e4f70428999 100644
--- a/src/backend/utils/cache/inval.c
+++ b/src/backend/utils/cache/inval.c
@@ -456,6 +456,8 @@ ProcessInvalidationMessages(InvalidationListHeader *hdr,
 {
 	ProcessMessageList(hdr->cclist, func(msg));
 	ProcessMessageList(hdr->rclist, func(msg));
+
+	ProcessPendingRelcacheRebuilds();
 }
 
 /*
diff --git a/src/backend/utils/cache/relcache.c b/src/backend/utils/cache/relcache.c
index 6125421d39a..927b8cef4d9 100644
--- a/src/backend/utils/cache/relcache.c
+++ b/src/backend/utils/cache/relcache.c
@@ -144,6 +144,14 @@ bool		criticalSharedRelcachesBuilt = false;
  */
 static long relcacheInvalsReceived = 0L;
 
+/*
+ * List of oids for entries that need to be rebuilt. Entries get queued onto
+ * it while receiving invalidations, and are processed at the end. This both
+ * avoids errors due to relcache rebuilds relying on an up2date relmapper, and
+ * avoids redundant rebuilds.
+ */
+static List *pending_rebuilds = NIL;
+
 /*
  * eoxact_list[] stores the OIDs of relations that (might) need AtEOXact
  * cleanup work.  This list intentionally has limited size; if it overflows,
@@ -251,7 +259,7 @@ static void RelationClearRelation(Relation relation, bool rebuild);
 
 static void RelationReloadIndexInfo(Relation relation);
 static void RelationReloadNailed(Relation relation);
-static void RelationFlushRelation(Relation relation);
+static void RelationFlushRelation(Relation relation, bool immed);
 static void RememberToFreeTupleDescAtEOX(TupleDesc td);
 static void AtEOXact_cleanup(Relation relation, bool isCommit);
 static void AtEOSubXact_cleanup(Relation relation, bool isCommit,
@@ -2556,7 +2564,7 @@ RelationClearRelation(Relation relation, bool rebuild)
  *	 This is used when we receive a cache invalidation event for the rel.
  */
 static void
-RelationFlushRelation(Relation relation)
+RelationFlushRelation(Relation relation, bool immed)
 {
 	if (relation->rd_createSubid != InvalidSubTransactionId ||
 		relation->rd_newRelfilenodeSubid != InvalidSubTransactionId)
@@ -2581,10 +2589,69 @@ RelationFlushRelation(Relation relation)
 		 */
 		bool		rebuild = !RelationHasReferenceCountZero(relation);
 
-		RelationClearRelation(relation, rebuild);
+		/*
+		 * Can't immediately rebuild entry - in the middle of receiving
+		 * invalidations relmapper might be out of date and point to an older
+		 * version of required catalogs. Defer rebuilds until the queue has
+		 * been emptied.
+		 */
+		if (rebuild && !immed)
+		{
+			MemoryContext oldcontext;
+
+			oldcontext = MemoryContextSwitchTo(CacheMemoryContext);
+			pending_rebuilds = lappend_oid(pending_rebuilds, RelationGetRelid(relation));
+			MemoryContextSwitchTo(oldcontext);
+
+			relation->rd_isvalid = false;
+		}
+		else
+			RelationClearRelation(relation, rebuild);
 	}
 }
 
+/*
+ * Rebuild relcache entries that have been marked as invalid and that need to
+ * to be rebuilt. This is separate from RelationFlushRelation() because
+ * relcache entries can only be rebuilt with an up2date relmapper, and because
+ * doing so allows us to avoid repeated rebuilds of the same entry.
+ */
+void
+ProcessPendingRelcacheRebuilds(void)
+{
+	List *pending = pending_rebuilds;
+	ListCell *lc;
+
+	/*
+	 * Clear out list of pending rebuilds before starting, new entries might
+	 * be queued while processing the current entries.
+	 *
+	 * XXX: What to do if we error out somewhere in the middle?
+	 */
+	pending_rebuilds = NIL;
+
+	if (IsTransactionState())
+	{
+		foreach(lc, pending)
+		{
+			Oid			relationId = lfirst_oid(lc);
+			Relation	relation;
+
+			RelationIdCacheLookup(relationId, relation);
+
+			/* nothing to do if if the entry since has been dropped */
+			if (!PointerIsValid(relation))
+				continue;
+
+			/* only rebuild if not already done so */
+			if (!relation->rd_isvalid)
+				RelationFlushRelation(relation, true);
+		}
+	}
+	list_free(pending);
+
+}
+
 /*
  * RelationForgetRelation - unconditionally remove a relcache entry
  *
@@ -2633,7 +2700,7 @@ RelationCacheInvalidateEntry(Oid relationId)
 	if (PointerIsValid(relation))
 	{
 		relcacheInvalsReceived++;
-		RelationFlushRelation(relation);
+		RelationFlushRelation(relation, false);
 	}
 }
 
diff --git a/src/include/utils/relcache.h b/src/include/utils/relcache.h
index dbbf41b0c16..4d867bda7d9 100644
--- a/src/include/utils/relcache.h
+++ b/src/include/utils/relcache.h
@@ -119,6 +119,8 @@ extern void RelationForgetRelation(Oid rid);
 
 extern void RelationCacheInvalidateEntry(Oid relationId);
 
+extern void ProcessPendingRelcacheRebuilds(void);
+
 extern void RelationCacheInvalidate(void);
 
 extern void RelationCloseSmgrByOid(Oid relationId);