Re: how could select id=xx so slow?

Yan Chunlu wrote:
> I have logged one day data and found the checkpoint is rather
frequently(detail:
> https://gist.github.com/3088338). Not sure if it is normal, but the
average time of checkpoint is
> about 100sec~200sec, it seems related with my settings:
>
> 574 checkpoint_segments = 64
> 575 wal_keep_segments = 5000
>
> I set checkpoint_segments as a very large value which is because
otherwise the slave server always can
> not follow the master, should I lower that value?

You mean, you set wal_keep_segments high for the standby, right?

wal_keep_segments has no impact on checkpoint frequency and intensity.

You are right that your checkpoint frequency is high. What is your value
of checkpoint_timeout?

You can increase the value of checkpoint_segments to decrease the
checkpoint frequence, but recovery will take longer then.

> or the slow query is about something else? thanks!

I guess the question is how saturated the I/O system is during
checkpoints. But even if it is very busy, I find it hard to believe
that such a trivial statement can take extremely long.

Yours,
Laurenz Albe