Ensure pg_filenode_relation(0, 0) returns NULL.

tglsfdc · tglsfdc · commit 1250aad42520 · 2021-06-12T13:29:24.000-04:00
Previously, a zero value for the relfilenode resulted in a confusing error message about "unexpected duplicate". This function returns NULL for other invalid relfilenode values, so zero should be treated likewise. It's been like this all along, so back-patch to all supported branches. Justin Pryzby Discussion: https://postgr.es/m/20210612023324.GT16435@telsasoft.com
diff --git a/src/backend/utils/adt/dbsize.c b/src/backend/utils/adt/dbsize.c
@@ -903,7 +903,11 @@ pg_filenode_relation(PG_FUNCTION_ARGS)
 {
 	Oid			reltablespace = PG_GETARG_OID(0);
 	Oid			relfilenode = PG_GETARG_OID(1);
-	Oid			heaprel = InvalidOid;
+	Oid			heaprel;
+
+	/* test needed so RelidByRelfilenode doesn't misbehave */
+	if (!OidIsValid(relfilenode))
+		PG_RETURN_NULL();
 
 	heaprel = RelidByRelfilenode(reltablespace, relfilenode);
 
