postgres index usage
Awesome article on understanding postgres performance had this little nugget, which gives you the tables in your database with the percentage of time they use an index:
SELECT
relname,
100 * idx_scan / (seq_scan + idx_scan) percent_of_times_index_used,
n_live_tup rows_in_table
FROM
pg_stat_user_tables
WHERE
seq_scan + idx_scan > 0
ORDER BY
n_live_tup DESC;