Ensure pg_filenode_relation(0, 0) returns NULL.

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
index 3c70bb59433ec35619453f62d41fdb7e06f0f41d..9c39e7d3b343aa16d066d2bf64f12b6d6e61bf6c 100644 (file)
--- 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);