On 2014-09-19 17:29:08 -0400, Robert Haas wrote: > > I generally have serious doubts about disabling it generally for > > read workloads. I imagine it e.g. will significantly penalize > > workloads where its likely that a cleanup lock can't be acquired > > every time... > > I share that doubt. But I understand why Simon wants to do something, > too, because the current situation is not great either.
Right, I totally agree. I doubt a simple approach like this will work in the general case, but I think something needs to be done. I think limiting the amount of HOT cleanup for readonly queries is a good idea, but I think it has to be gradual. Say after a single cleaned up page at least another 500 pages need to have been touched till the next hot cleanup. That way a single query won't be penalized with cleaning up everything, but there'll be some progress. The other thing I think might be quite worthwile would be to abort hot cleanup when the gain is only minimal. If e.g. only 1 small tuple is removed from a half full page it's not worth the cost of the wal logging et al. Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
