pg_filenode_relation ( tablespace oid, filenode oid ) → regclassReturns a relation's OID given the tablespace OID and filenode it is stored under. This is essentially the inverse mapping of
pg_relation_filepath. For a relation in the database's default tablespace, the tablespace can be specified as zero. Returns NULL if no relation in the current database is associated with the given values, or if dealing with a temporary relation.