This utility allows administrators to view the file structure used by
PostgreSQL.  Databases are placed in directories based on their OIDs in
pg_database, and the tables in that directory are named by original
OIDs, stored in pg_class.relfilenode.  Oid2name connects to the database
and extracts the OID and table name information.

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It can be used in four ways:


oid2name

  This will connect to the template1 database and display all databases
  in the system:

  $ oid2name
  All databases:
  ---------------------------------
  18720  = test1
  1      = template1
  18719  = template0
  18721  = test
  18735  = postgres
  18736  = cssi


oid2name -d test [-x]

  This connects to the database test and shows all tables and their OIDs:

  $ oid2name -d test
  All tables from database "test":
  ---------------------------------
  18766  = dns
  18737  = ips
  18722  = testdate


oid2name -d test -o 18737
oid2name -d test -t testdate

  This will connect to the database test and display the table name for oid
  18737 and the oid for table name testdate respectively:

  $ oid2name -d test -o 18737
  Tablename of oid 18737 from database "test":
  ---------------------------------
  18737  = ips


  $ oid2name -d test -t testdate 
  Oid of table testdate from database "test":
  ---------------------------------
  18722  = testdate

Keep in mind tables over one gigabyte will be split into separate files
with numeric file extensions.

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Sample session:

$ cd /u/pg/data/base
$ oid2name
All databases:
---------------------------------
16817  = test2
16578  = x
16756  = test
1      = template1
16569  = template0
16818  = test3
16811  = floattest

$ cd 16756
$ ls 1873*
18730   18731   18732   18735   18736   18737   18738   18739

$ oid2name -d test -o 18737
Tablename of oid 18737 from database "test":
---------------------------------
18737  = ips

$ oid2name -d test -t ips
Oid of table ips from database "test":
---------------------------------
18737  = ips

$ # show disk space for every db object
$ du * | while read SIZE OID
> do
>	echo "$SIZE      `oid2name -q -d test -o $OID`"
> done
24      18737  = ips
36      18722  = cities
...

$ # same as above, but sort by largest first
$ du * | while read SIZE OID
> do
>	echo "$SIZE      `oid2name -q -d test -o $OID`"
> done |
> sort -rn
2048    19324  = bigtable
1950    23903  = customers
...

$ # show disk usage per database
$ cd /u/pg/data/base
$ du -s * |
> while read SIZE OID
> do
>	echo "$SIZE      `aspg oid2name -q | grep ^$OID' '`"
> done |
> sort -rn
2256        18721  = test
2135        18735  = postgres
..

This can be done in psql with:  

test=> SELECT relpages, relfilenode, relname FROM pg_class ORDER BY relpages DESC;

Each page is typically 8k.  Relpages is updated by VACUUM.

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Mail me with any problems or additions you would like to see.  Clearing 
house for the code will be at:  http://www.crimelabs.net

b. palmer, bpalmer@crimelabs.net