postgres/contrib/dbsize

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_tablespace_size(oid)
	int8 pg_relation_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, and support databases and tables. Please
note that relation_size() only reports table file usage and not the
space used by indexes and toast tables.

Functions using oids are:
	
	SELECT pg_database_size(1);         -- template1 database
	SELECT pg_tablespace_size(1663);    -- pg_default tablespace
	SELECT pg_relation_size(1259);      -- pg_class table size

pg_relation_size() will report the size of the table, index and toast
table OIDs, but they must be requested individually. To obtain the total
size of a table including all helper files you'd have to do something
like:

XXX This query does not work, syntax error XXX
	
	SELECT pg_relation_size(cl.oid) AS tablesize,
	       CASE WHEN reltoastrelid=0 THEN 0
	            ELSE pg_relation_size(reltoastrelid) END AS toastsize,
	       SUM(pg_relation_size(indexrelid)) AS indexsize,
	       pg_size_pretty(pg_relation_size(cl.oid)
	                    + pg_relation_size(reltoastrelid)
	                    + SUM(pg_relation_size(indexrelid))::int8) 
								AS totalsize
	  FROM pg_class cl
	  JOIN pg_index ON cl.oid=indrelid
	 WHERE relname = 'pg_rewrite'
	 GROUP BY 1,2

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.  Finally, load the functions
into any database using dbsize.sql.