PostgreSQL load driven up by overzealous pruning of old ipdevpoll_job_log entries in NAV 4.2.5

[Morten Brekkevold]

NAV 4.2.5 introduced a fix for bug logging. In conjunction with this, a different regime for pruning old entries from the ipdevpoll_job_log tables was introduced.

Pruning is done via the trigger `trig_trim_old_ipdevpoll_job_log_entries_on_insert`, which runs on every insert, but performs a full table clean on about 20% of inserts by use of the RANDOM() function.

The full table clean statement is quite costly on a large table, and running for 20% of INSERTs has proven too ambitious, since this means 20% of inserts to this table will be unbearably slow.

Of course, this basically amounts to log rotation, and doesn't really belong in a trigger. It should run periodically, outside of the database, and independent of inserts to the table.

[Morten Brekkevold (mbrekkevold)]

fixed a week ago: https://nav.uninett.no/hg/stable/rev/278105419e81