Размер таблиц в postgres

см. прочие поля в таблице.

SELECT oid,
       table_schema,
       table_name,
       total_bytes,
       pg_size_pretty(total_bytes) AS humna_size
  FROM (
  SELECT *, total_bytes-index_bytes-COALESCE(toast_bytes,0) AS table_bytes FROM (
      SELECT c.oid,nspname AS table_schema, relname AS TABLE_NAME
              , c.reltuples AS row_estimate
              , pg_total_relation_size(c.oid) AS total_bytes
              , pg_indexes_size(c.oid) AS index_bytes
              , pg_total_relation_size(reltoastrelid) AS toast_bytes
          FROM pg_class c
          LEFT JOIN pg_namespace n ON n.oid = c.relnamespace
          WHERE relkind = 'r'
  ) a
) a
-- where round(total_bytes/1024/1024) > 100 -- только если размер больше 100Мб
order by total_bytes desc