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oid2name is a utility program that helps administrators to examine the file structure used by PostgreSQL. To make use of it, you need to be familiar with the database file structure, which is described in Chapter 53.
Note: The name "oid2name" is historical, and is actually rather misleading, since most of the time when you use it, you will really be concerned with tables' filenode numbers (which are the file names visible in the database directories). Be sure you understand the difference between table OIDs and table filenodes!
oid2name connects to a target database and extracts OID, filenode, and/or table name information. You can also have it show database OIDs or tablespace OIDs. The program is controlled by a large number of command-line switches, as shown in Table F-13.
Table F-13. oid2name switches
| Switch | Description |
|---|---|
| -o oid | show info for table with OID oid |
| -f filenode | show info for table with filenode filenode |
| -t tablename_pattern | show info for table(s) matching tablename_pattern |
| -s | show tablespace OIDs |
| -S | include system objects (those in information_schema, pg_toast and pg_catalog schemas) |
| -i | include indexes and sequences in the listing |
| -x | display more information about each object shown: tablespace name, schema name, and OID |
| -q | omit headers (useful for scripting) |
| -d database | database to connect to |
| -H host | database server's host |
| -p port | database server's port |
| -U username | username to connect as |
To display specific tables, select which tables to show by using -o, -f and/or -t. -o takes an OID, -f takes a filenode, and -t takes a tablename (actually, it's a LIKE pattern, so you can use things like foo%). You can use as many of these switches as you like, and the listing will include all objects matched by any of the switches. But note that these switches can only show objects in the database given by -d.
If you don't give any of -o, -f or -t, but do give -d, it will list all tables in the database named by -d. In this mode, the -S and -i switches control what gets listed.
If you don't give -d either, it will show a listing of database OIDs. Alternatively you can give -s to get a tablespace listing.
$ # what's in this database server, anyway?
$ oid2name
All databases:
Oid Database Name Tablespace
----------------------------------
17228 alvherre pg_default
17255 regression pg_default
17227 template0 pg_default
1 template1 pg_default
$ oid2name -s
All tablespaces:
Oid Tablespace Name
-------------------------
1663 pg_default
1664 pg_global
155151 fastdisk
155152 bigdisk
$ # OK, let's look into database alvherre
$ cd $PGDATA/base/17228
$ # get top 10 db objects in the default tablespace, ordered by size
$ ls -lS * | head -10
-rw------- 1 alvherre alvherre 136536064 sep 14 09:51 155173
-rw------- 1 alvherre alvherre 17965056 sep 14 09:51 1155291
-rw------- 1 alvherre alvherre 1204224 sep 14 09:51 16717
-rw------- 1 alvherre alvherre 581632 sep 6 17:51 1255
-rw------- 1 alvherre alvherre 237568 sep 14 09:50 16674
-rw------- 1 alvherre alvherre 212992 sep 14 09:51 1249
-rw------- 1 alvherre alvherre 204800 sep 14 09:51 16684
-rw------- 1 alvherre alvherre 196608 sep 14 09:50 16700
-rw------- 1 alvherre alvherre 163840 sep 14 09:50 16699
-rw------- 1 alvherre alvherre 122880 sep 6 17:51 16751
$ # I wonder what file 155173 is ...
$ oid2name -d alvherre -f 155173
From database "alvherre":
Filenode Table Name
----------------------
155173 accounts
$ # you can ask for more than one object
$ oid2name -d alvherre -f 155173 -f 1155291
From database "alvherre":
Filenode Table Name
-------------------------
155173 accounts
1155291 accounts_pkey
$ # you can mix the options, and get more details with -x
$ oid2name -d alvherre -t accounts -f 1155291 -x
From database "alvherre":
Filenode Table Name Oid Schema Tablespace
------------------------------------------------------
155173 accounts 155173 public pg_default
1155291 accounts_pkey 1155291 public pg_default
$ # show disk space for every db object
$ du [0-9]* |
> while read SIZE FILENODE
> do
> echo "$SIZE `oid2name -q -d alvherre -i -f $FILENODE`"
> done
16 1155287 branches_pkey
16 1155289 tellers_pkey
17561 1155291 accounts_pkey
...
$ # same, but sort by size
$ du [0-9]* | sort -rn | while read SIZE FN
> do
> echo "$SIZE `oid2name -q -d alvherre -f $FN`"
> done
133466 155173 accounts
17561 1155291 accounts_pkey
1177 16717 pg_proc_proname_args_nsp_index
...
$ # If you want to see what's in tablespaces, use the pg_tblspc directory
$ cd $PGDATA/pg_tblspc
$ oid2name -s
All tablespaces:
Oid Tablespace Name
-------------------------
1663 pg_default
1664 pg_global
155151 fastdisk
155152 bigdisk
$ # what databases have objects in tablespace "fastdisk"?
$ ls -d 155151/*
155151/17228/ 155151/PG_VERSION
$ # Oh, what was database 17228 again?
$ oid2name
All databases:
Oid Database Name Tablespace
----------------------------------
17228 alvherre pg_default
17255 regression pg_default
17227 template0 pg_default
1 template1 pg_default
$ # Let's see what objects does this database have in the tablespace.
$ cd 155151/17228
$ ls -l
total 0
-rw------- 1 postgres postgres 0 sep 13 23:20 155156
$ # OK, this is a pretty small table ... but which one is it?
$ oid2name -d alvherre -f 155156
From database "alvherre":
Filenode Table Name
----------------------
155156 foo
oid2name requires a running database server with non-corrupt system catalogs. It is therefore of only limited use for recovering from catastrophic database corruption situations.
B. Palmer <[email protected]>