On 2014-10-30 14:51:54 -0400, Robert Haas wrote: > On Wed, Oct 29, 2014 at 2:36 PM, Tomas Vondra <t...@fuzzy.cz> wrote: > >> I would tend not to worry too much about this case. I'm skeptical > >> that there are a lot of people using large template databases. But > >> if there are, or if some particular one of those people hits this > >> problem, then they can raise checkpoint_segments to avoid it. The > >> reverse problem, which you are encountering, cannot be fixed by > >> adjusting settings. > > > > That however solves "only" the checkpoint, not the double amount of I/O > > due to writing both the files and WAL, no? But maybe that's OK. > > I mean, it's not unimaginable that it's going to hurt somebody, but > the current situation is pretty bad too. You don't have to be the > world's foremost PostgreSQL performance expert to know that extra > checkpoints are really bad for performance. Write volume is of course > also a problem, but I bet there are a lot more people using small > template databases (where the write volume isn't really an issue, > because as Heikki points out the checkpoint wastes half a segment > anyway, but the checkpoint may very well be a issue) than large ones > (where either could be an issue).
Agreed. The current behaviour is a pretty ugly that just failed to fail recently. I actually think we should *always* use the new code and not add a separate wal_level=minimal branch. Maintaining this twice just isn't worth the effort. minimal is used *far* less these days. Greetings, Andres Freund -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
