On 10/30/2014 08:51 PM, 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).
Nitpick: I didn't say that a a checkpoint wastes half a segment. An xlog
switch does, but a checkpoint doesn't automatically cause an xlog switch.
But I agree with the sentiment in general.
- Heikki
--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers
