Don't allow relminmxid to go backwards during VACUUM FULL

alvherre · alvherre · commit b7e51d9c06e6 · 2014-06-27T14:43:46.000-04:00
We were allowing a table's pg_class.relminmxid value to move backwards when heaps were swapped by VACUUM FULL or CLUSTER. There is a similar protection against relfrozenxid going backwards, which we neglected to clone when the multixact stuff was rejiggered by commit 0ac5ad5. Backpatch to 9.3, where relminmxid was introduced. As reported by Heikki in http://www.postgresql.org/message-id/52401AEA.9000608@vmware.com
diff --git a/src/backend/commands/cluster.c b/src/backend/commands/cluster.c
@@ -861,6 +861,12 @@ copy_heap_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex, bool verbose,
 	if (TransactionIdPrecedes(FreezeXid, OldHeap->rd_rel->relfrozenxid))
 		FreezeXid = OldHeap->rd_rel->relfrozenxid;
 
+	/*
+	 * MultiXactCutoff, similarly, shouldn't go backwards either.
+	 */
+	if (MultiXactIdPrecedes(MultiXactCutoff, OldHeap->rd_rel->relminmxid))
+		MultiXactCutoff = OldHeap->rd_rel->relminmxid;
+
 	/* return selected values to caller */
 	*pFreezeXid = FreezeXid;
 	*pCutoffMulti = MultiXactCutoff;
