pg_relation_filenode()
A function for obtaining the filenode number of a relation
pg_relation_filenode() is a system function for obtaining the filenode number of a relation with the specified OID or name.
pg_relation_filenode() was added in PostgreSQL 9.0.
Usage
pg_relation_filenode (relationregclass) →oid
The returned oid corresponds to the value contained in relfilenode in pg_class, except for certain system catalog tables where the value is 0. It is therefpre necessary to use this function to reliably determine a relations's filenode.
NULL is returned if the relation is a type such as a view which is does not have on-disk storage.
Change history
- PostgreSQL 9.0
- added (commit b9b8831a)
Examples
postgres=# SELECT pg_relation_filenode('foo');
pg_relation_filenode
----------------------
16499
(1 row)
Attempting to query the relation filenode of a non-existent relation:
postgres=# SELECT pg_relation_filenode('bar');
ERROR: relation "bar" does not exist
LINE 1: SELECT pg_relation_filenode('bar');
Attempting to query the relation filenode of a relation which does not store data:
postgres=# CREATE VIEW bar AS SELECT * FROM foo; CREATE VIEW postgres=# SELECT pg_relation_filenode('bar') IS NULL; ?column? ---------- t (1 row)
See filenode for further examples.
References
- PostgreSQL documentation: Database Object Location Functions
Useful links
- The mapping of oid and relfilenode in PG - January 2021 blog article by HighGo
