I think you can check n_dead_tup, n_mod_since_analyze from pg_stat_all_tables, and see if the numbers are high, then it would be a good idea to perform vacuum. I found some query on the net which might help you. See https://gist.github.com/lesovsky/b0e4033380b0992789118ab35c4... I think you might need to change this depending on the version of Postgres.