IMPORTANT NOTE This has been already addressed in PostgreSQL core, but this option is still available in RDS. What does it change and why is so important? Tracking databases and not just tables counters in Postgres isn’t cheap, but since some time ago there were workarounds involving the setup of a ramdisk to place the directory pointed by stat_temp_directory GUC variable. That directory places a global.stat and a per-database stat files called like db_<oidOfDB>.