All supertables

WITH tables_in_inheritance_hierarchy AS (SELECT pn.nspname AS parent_schema, p.oid AS parent_oid, p.relname AS parent_table, pi.inhrelid AS child_oid
FROM pg_inherits pi INNER JOIN pg_class p ON pi.inhparent=p.oid
INNER JOIN pg_namespace pn ON p.relnamespace=pn.oid
INNER JOIN pg_authid AS ap ON pn.nspowner=ap.oid
WHERE (pn.nspname='public' OR ap.rolname<>'postgres'))
SELECT parent_schema, parent_table, Count(*) AS number_of_direct_children
FROM tables_in_inheritance_hierarchy AS tih
WHERE NOT EXISTS (SELECT 1
FROM tables_in_inheritance_hierarchy AS tih_check 
WHERE tih.parent_oid=tih_check.child_oid)
GROUP BY parent_schema, parent_table
ORDER BY Count(*) DESC, parent_schema, parent_table;