The largestTables PostgreSQL function.

largestTables.sql

CREATE OR REPLACE FUNCTION public."largestTables" (
)
RETURNS TABLE (
  relation text,
  size text
) AS
$body$
BEGIN

-- http://wiki.postgresql.org/wiki/Disk_Usage
RETURN QUERY SELECT nspname || '.' || relname AS "relation",
    pg_size_pretty(pg_relation_size(C.oid)) AS "size"
  FROM pg_class C
  LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)
  WHERE nspname NOT IN ('pg_catalog', 'information_schema')
  ORDER BY pg_relation_size(C.oid) DESC
  LIMIT 20;

END;
$body$
LANGUAGE 'plpgsql'
STABLE
CALLED ON NULL INPUT
SECURITY INVOKER
COST 10 ROWS 20;

COMMENT ON FUNCTION public."largestTables"()
IS 'Run a query returning the size of the largest tables and indexes.
See http://wiki.postgresql.org/wiki/Disk_Usage.';