filenode_map_inspect

A simple extension providing functionality to check and examine the pg_filenode.map files present in PostgreSQL.

This is an experimental extension for educational and diagnostic purposes only. USE AT YOUR OWN RISK!

Requirements

This extension will compile with all PostgreSQL versions from 9.0 (where pg_filenode.map was introduced).

Functions

• filenode_map_check(): lists the location of all pg_filenode.map files present in the database cluster, and verifies their status.

• filenode_map_list(): lists name, oid and filenode of entries in the current database's pg_filenode.map file

• filenode_map_list_global(): lists name, oid and filenode entries in the global pg_filenode.map file

Examples

Output of filenode_map_check():

postgres=# SELECT * FROM filenode_map_check();
WARNING:  could not read file "base/32774/pg_filenode.map": read 256 of 512
 database  |            file            |       state
-----------+----------------------------+-------------------
 postgres  | base/12630/pg_filenode.map | OK
 template1 | base/1/pg_filenode.map     | OK
 template0 | base/12629/pg_filenode.map | OK
 foo       | base/32774/pg_filenode.map | FILE_ACCESS_ERROR
(4 rows)

Here we see the filenode map for database foo is incomplete. We could establish exactly the same result by attempting to connect to foo. The advantage of this function is that (assuming at least one database can be connected to) it will present an overview of the state of all database pg_filenode.map files.

Output of filenode_map_list():

repmgr=# SELECT * FROM filenode_map_list();
			  relname              | oid  | filenode
-----------------------------------+------+----------
 pg_class                          | 1259 |     1259
 pg_attribute                      | 1249 |     1249
 pg_proc                           | 1255 |     1255
 pg_type                           | 1247 |     1247
 pg_toast_1255                     | 2836 |     2836
 pg_toast_1255_index               | 2837 |     2837
 pg_attribute_relid_attnam_index   | 2658 |     2658
 pg_attribute_relid_attnum_index   | 2659 |     2659
 pg_class_oid_index                | 2662 |     2662
 pg_class_relname_nsp_index        | 2663 |     2663
 pg_class_tblspc_relfilenode_index | 3455 |     3455
 pg_proc_oid_index                 | 2690 |     2690
 pg_proc_proname_args_nsp_index    | 2691 |     2691
 pg_type_oid_index                 | 2703 |     2703
 pg_type_typname_nsp_index         | 2704 |     2704
(15 rows)

Notes

The practical utility of this extension is debatable.

In practice, cases of pg_filenode.map corruption appear to be seldom and usually self-inflicted.

See also

• source code: src/backend/utils/cache/relmapper.c
• Decoding pg_filenode.map files with pg_filenodemapdata