From: | Craig Ringer <ringerc(at)ringerc(dot)id(dot)au> |
---|---|
To: | Yan Chunlu <springrider(at)gmail(dot)com> |
Cc: | Albe Laurenz <laurenz(dot)albe(at)wien(dot)gv(dot)at>, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: how could select id=xx so slow? |
Date: | 2012-07-10 01:25:33 |
Message-ID: | 4FFB848D.7080900@ringerc.id.au |
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Lists: | pgsql-performance |
On 07/09/2012 05:20 PM, Yan Chunlu wrote:
>
> the value of "log_min_messages" in postgresql.conf is error, I have
> changed it to "warning", so far does not received any warning, still
> waiting.
When trying to track down performance issues, increasing logging to at
least `info' would seem to be sensible.
I suggest increasing your logging and enabling the auto_explain module
so it logs slow queries. If you can afford the substantial performance
hit you could enable its analyze mode to get details on why.
>
> beside I do see some COMMIT which is relatively slow for example:
> 60 2012-07-08 00:00:29 CST [19367]: [131-1] LOG: duration: 375.851
> ms statement: COMMIT
> 61 2012-07-08 00:00:30 CST [19367]: [132-1] LOG: duration: 327.964
> ms statement: COMMIT
That certainly is slow. Again, I suspect checkpoint activity could be at
fault. You may need to tune to spread your checkpoints out and use more
aggressive bgwriter settings. See the wiki for performance tuning info.
>
> but only one "BEGIN" in the same one day log file, did that influence
> the query time too?
Only one BEGIN in the whole day? Or do you mean "only one BEGIN slow
enough to trigger slow query logging" ?
Do you have a "log_min_duration_statement" directive set in your
postgresql.conf ?
--
Craig Ringer
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