Do not leave out the referential constraints (islands)

SELECT nc.nspname AS table_schema, c.relname AS table_name
FROM pg_class AS c INNER JOIN pg_namespace AS nc ON c.relnamespace=nc.oid
INNER JOIN pg_authid AS a ON nc.nspowner=a.oid
WHERE (nc.nspname='public' OR rolname<>'postgres')
AND c.relkind='r'
AND NOT EXISTS (SELECT *
FROM pg_constraint
WHERE contype='f'
AND pg_constraint.confrelid=c.oid)
AND NOT EXISTS (SELECT *
FROM pg_constraint
WHERE contype='f'
AND pg_constraint.conrelid=c.oid)
AND NOT EXISTS (SELECT *
FROM pg_inherits pi
WHERE pi.inhparent=c.oid)
ORDER BY table_schema, table_name;