Re: slow "select count(*) from information_schema.tables;" in some cases - Mailing list pgsql-performance

Lars Aksel Opsahl <Lars.Opsahl@nibio.no> writes:
>> SELECT relname, pg_size_pretty(pg_relation_size(C.oid)) FROM pg_class C LEFT JOIN pg_namespace N ON (N.oid =
C.relnamespace)WHERE nspname = 'pg_catalog' ORDER BY 2 DESC LIMIT 20; can you show the output of this query 

"ORDER BY 2" is giving you a textual sort of the sizes, which is entirely
unhelpful.  Try

SELECT relname, pg_size_pretty(pg_relation_size(C.oid)) FROM pg_class C LEFT JOIN pg_namespace N ON (N.oid =
C.relnamespace)WHERE nspname = 'pg_catalog' ORDER BY pg_relation_size(C.oid) DESC LIMIT 20; 

            regards, tom lane