OID2NAME(1)

💅 OID2NAME(1) — bestie edition ✨

ok so this is oid2name, straight out of the PostgreSQL 14.24 Documentation, and we're gonna get into it 🎀

🌸 NAME

oid2name — resolves OIDs and file nodes in a PostgreSQL data directory 🦋

✨ SYNOPSIS

oid2name [option...]

💖 DESCRIPTION

okay so oid2name is this utility program that helps admins peek at the file structure PostgreSQL actually uses 👀. To actually get anything out of it you gotta be familiar with the database file structure — that whole thing is described in Chapter 70, iykyk.

🚨 Note — the name "oid2name" is historical, and honestly it's kind of misleading, because most of the time when you use it you're really concerned with tables' filenode numbers (which are, literally, the file names you see in the database directories). Be sure you understand the difference between table OIDs and table filenodes! fr fr, don't skip this 💀

So what does it do? oid2name connects to a target database and extracts OID, filenode, and/or table name information. And you can also have it show database OIDs or tablespace OIDs. slay 💅

🎀 OPTIONS

oid2name accepts the following command-line arguments:

• -f filenode, --filenode=filenode — show info for the table with filenode filenode.
• -i, --indexes — include indexes and sequences in the listing.
• -o oid, --oid=oid — show info for the table with OID oid.
• -q, --quiet — omit headers (useful for scripting 👑).
• -s, --tablespaces — show tablespace OIDs.
• -S, --system-objects — include system objects (those in information_schema, pg_toast and pg_catalog schemas).
• -t tablename_pattern, --table=tablename_pattern — show info for table(s) matching tablename_pattern.
• -V, --version — Print the oid2name version and exit.
• -x, --extended — display more information about each object shown: tablespace name, schema name, and OID.
• -?, --help — Show help about oid2name command line arguments, and exit.

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🫶 connection parameter options (yes, another list, stay with me)

oid2name also accepts the following command-line arguments for connection parameters:

• -d database, --dbname=database — database to connect to.
• -h host, --host=host — database server's host.
• -H host — database server's host. Use of this parameter is deprecated as of PostgreSQL 12 ⚠️ (yeah, it's giving legacy, use -h instead).
• -p port, --port=port — database server's port.
• -U username, --username=username — user name to connect as.

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🧚 how the selection actually works

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 table name (actually, it's a LIKE pattern, so you can use things like foo%). You can use as many of these options as you like, and the listing will include all objects matched by any of the options 🔥. But note that these options 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 options 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. cute, right? 🎀

🌈 ENVIRONMENT

• PGHOST
• PGPORT
• PGUSER

— Default connection parameters.

This utility, like most other PostgreSQL utilities, also uses the environment variables supported by libpq (see Section 34.15) 💜.

The environment variable PG_COLOR specifies whether to use color in diagnostic messages. Possible values are always, auto and never.

😭 NOTES

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 💀. Like, if everything's on fire, this is not your fire extinguisher, bestie.

⭐ EXAMPLES

okay this is the fun part, buckle up 🦋

$ # 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

👑 AUTHOR

B. Palmer <bpalmer@crimelabs.net>

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and that's the whole page, no cap 🫶 this was PostgreSQL 14.24, dated 2026 — OID2NAME(1), signing off 💜✨