Get all table/partition sizes

get_table_partitions_sizes.sql

SELECT nspname || '.' || relname AS "relation",
       pg_size_pretty(pg_total_relation_size(C.oid)) AS "total_size"
FROM pg_class C
         LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)
         LEFT OUTER JOIN pg_inherits I ON (C.relfilenode = I.inhrelid OR C.relfilenode = I.inhparent)
WHERE nspname NOT IN ('pg_catalog', 'information_schema')
  AND C.relkind <> 'i'
  AND nspname !~ '^pg_toast'
  AND I.inhrelid is null
UNION ALL
select nspname || '.' || relname AS "relation",
       pg_size_pretty(sum(pg_relation_size(inhrelid))) AS "total_size"
FROM pg_inherits  I
         LEFT JOIN pg_class C ON (C.oid = I.inhparent)
         LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)
GROUP BY  nspname,relname
ORDER BY 1,2

-- https://dba.stackexchange.com/a/134574