Show relation size in Postgres

postgres_relation_size.sql

-- Relations, as in, tables and indexes

SELECT nspname || '.' || relname AS "relation",
       pg_size_pretty(pg_relation_size(PC.oid)) AS "size"
FROM pg_class PC
LEFT JOIN pg_namespace NS ON (NS.oid = PC.relnamespace)
WHERE nspname NOT IN ('pg_catalog', 'information_schema') 
  AND nspname !~ '^pg_toast'
ORDER BY pg_relation_size(PC.oid) DESC