Get total size for all Postgres or Greenplum tables including partitions
Here is what i have, its also a little bit roundabout and not testet in PG8.2 
(not supported anymore ;) ) but it shows your schema.tablename,PrettySize (first Select) and  partitioned Tables are grouped to one (ParentTablename) (second Select). its maybe not the best solution (Tuning welcome)

--get all tables sizes and group partitioned tables by PartenTablename
SELECT nspname || '.' || relname AS "relation",
       pg_size_pretty(pg_total_relation_size(C.oid)) AS "total_size"
FROM pg_class C
LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)
LEFT OUTER JOIN pg_inherits I ON (C.relfilenode = I.inhrelid OR C.relfilenode = I.inhparent)
WHERE nspname NOT IN ('pg_catalog', 'information_schema')
    AND C.relkind &lt;&gt; 'i'
    AND nspname !~ '^pg_toast'
    AND I.inhrelid is null
UNION ALL
select nspname || '.' || relname AS "relation", 
       pg_size_pretty(sum(pg_relation_size(inhrelid))) AS "total_size" 
FROM pg_inherits  I 
LEFT JOIN pg_class C ON (C.oid = I.inhparent)
LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)  
GROUP BY  nspname,relname
ORDER BY 1,2