This module contains several functions that report the on-disk size of a 
given database object in bytes:

	int8 database_size(name)
	int8 relation_size(text)
	int8 indexes_size(text)
	int8 total_relation_size(text)

	int8 pg_database_size(oid)
	int8 pg_relation_size(oid)
	int8 pg_tablespace_size(oid)

	text pg_size_pretty(int8)

	setof record relation_size_components(text)

The first four functions take the name of the object (possibly 
schema-qualified for the latter three) and returns the size of the
on-disk files in bytes.

	SELECT database_size('template1');
	SELECT relation_size('pg_class');
	SELECT indexes_size('pg_class');
	SELECT total_relation_size('pg_class');

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

The indexes_size() function returns the total size of the indices for a 
relation, including any toasted indices.

The total_relation_size() function returns the total size of the relation,
all its indices, and any toasted data.  

Please note that relation_size and pg_relation_size report only the size of
the selected relation itself; any related indexes or toast tables are not
counted.  To obtain the total size of a table including all indices and
toasted data, use total_relation_size().

The last function, relation_size_components(), returns a set of rows
showing the sizes of the component relations constituting the input 
relation.  

Examples
========

I've loaded the following table with a little less than 3 MB of data for 
illustration:

    create table fat ( id serial, data varchar );
    create index fat_uidx on fat (id);
    create index fat_idx on fat (data);

You can retrieve a rowset containing constituent sizes as follows:

# SELECT relation_size_components('fat');
              relation_size_components              
----------------------------------------------------
 (2088960,65536,2891776,fat,r,59383,59383)
 (32768,704512,737280,pg_toast_59383,t,59386,59386)
 (0,32768,32768,pg_toast_59383_index,i,59388,59388)
 (0,2039808,2039808,fat_idx,i,59389,59389)
 (0,49152,49152,fat_uidx,i,59911,59911)
(5 rows)

To see a more readable output of the rowset:

    SELECT * 
    FROM relation_size_components('fat') AS (idxsize BIGINT, 
                                             datasize BIGINT, 
                                             totalsize BIGINT, 
                                             relname NAME, 
                                             kind "char", 
                                             relid OID, 
                                             node OID) 
    ORDER BY totalsize;

 idxsize | datasize | totalsize |       relname        | kind | relid | node  
---------+----------+-----------+----------------------+------+-------+-------
       0 |    32768 |     32768 | pg_toast_59383_index | i    | 59388 | 59388
       0 |    49152 |     49152 | fat_uidx             | i    | 59911 | 59911
   32768 |   704512 |    737280 | pg_toast_59383       | t    | 59386 | 59386
       0 |  2039808 |   2039808 | fat_idx              | i    | 59389 | 59389
 2088960 |    65536 |   2891776 | fat                  | r    | 59383 | 59383
(5 rows)

To see the sum total size of a relation:

# select total_relation_size('fat');
 total_relation_size 
-------------------------
                 2891776
(1 row)

To see just the size of the uncompressed relation data:

# select relation_size('fat');
 relation_size 
---------------
         65536
(1 row)

To see the size of all related indices:

# select indexes_size('fat');
 indexes_size 
--------------
      2088960
(1 row)

To install, just run make; make install.  Then load the functions
into any database using dbsize.sql.