/* The size of indexes, descending by size */
SELECT
c.relname AS name, pg_size_pretty(sum(c.relpages::bigint*8192)::bigint) AS size
FROM
pg_class c
LEFT JOIN
pg_namespace n ON (n.oid = c.relnamespace)
WHERE
n.nspname NOT IN ('pg_catalog', 'information_schema') AND n.nspname !~ '^pg_toast' AND c.relkind='i'
GROUP BY
c.relname
ORDER BY
sum(c.relpages) DESC;