pg_tab_size.sql

select
    nspname || '.' || relname as "relation",
    pg_size_pretty(
        pg_relation_size(C.oid)
    ) as "size",
    to_char(round( pg_relation_size(C.oid) /(
        select
            sum( pg_relation_size( C.oid ) ) as "totalsize"
        from
            pg_class C
    ) * 100.0, 2), '90.00' ) percentage
from
    pg_class C left join pg_namespace N on
    (
        N.oid = C.relnamespace
    )
where
    nspname not in(
        'pg_catalog',
        'information_schema'
    )
    and pg_relation_size(C.oid) > 100000
order by
    pg_relation_size(C.oid) desc limit 50;