postgresql/contrib/dbsize/README.dbsize

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This module contains several functions that report the size of a given
database object:
int8 database_size(name)
int8 relation_size(text)
int8 pg_database_size(oid)
int8 pg_relation_size(oid)
int8 pg_tablespace_size(oid)
text pg_size_pretty(int8)
The first two functions:
SELECT database_size('template1');
SELECT relation_size('pg_class');
take the name of the object (possibly schema-qualified, for relation_size),
while these functions take object OIDs:
SELECT pg_database_size(1); -- template1 database
SELECT pg_relation_size(1259); -- pg_class table size
SELECT pg_tablespace_size(1663); -- pg_default tablespace
Please note that relation_size and pg_relation_size report only the size of
the selected relation itself; any subsidiary indexes or toast tables are not
counted. To obtain the total size of a table including all helper files
you'd have to do something like:
SELECT *,
pg_size_pretty(tablesize+indexsize+toastsize+toastindexsize) AS totalsize
FROM
(SELECT pg_relation_size(cl.oid) AS tablesize,
COALESCE((SELECT SUM(pg_relation_size(indexrelid))::bigint
FROM pg_index WHERE cl.oid=indrelid), 0) AS indexsize,
CASE WHEN reltoastrelid=0 THEN 0
ELSE pg_relation_size(reltoastrelid)
END AS toastsize,
CASE WHEN reltoastrelid=0 THEN 0
ELSE pg_relation_size((SELECT reltoastidxid FROM pg_class ct
WHERE ct.oid = cl.reltoastrelid))
END AS toastindexsize
FROM pg_class cl
WHERE relname = 'foo') ss;
This sample query utilizes the helper function pg_size_pretty(int8),
which formats the number of bytes into a convenient string using KB, MB,
GB. It is also contained in this module.
To install, just run make; make install. Then load the functions
into any database using dbsize.sql.