Re: Any better plan for this query?.. - Mailing list pgsql-performance

From Simon Riggs
Subject Re: Any better plan for this query?..
Date
Msg-id 1242128981.3843.257.camel@ebony.2ndQuadrant
Whole thread Raw
In response to Re: Any better plan for this query?..  (Dimitri <dimitrik.fr@gmail.com>)
Responses Re: Any better plan for this query?..
List pgsql-performance
On Tue, 2009-05-12 at 12:19 +0200, Dimitri wrote:

> What I'm trying to do now is to understand what exactly is the
> problem.

You're running with 1600 users, which is above the scalability limit
uncovered (by Sun...) during earlier benchmarking. The scalability
issues are understood but currently considered above the
reasonable-setting limit and so nobody has been inclined to improve
matters.

You should use a connection concentrator to reduce the number of
sessions down to say 400.

You're WAL buffers setting is also too low and you will be experiencing
contention on the WALWriteLock. Increase wal_buffers to about x8 where
you have it now.

You can move pg_xlog to its own set of drives.

Set checkpoint_completion_target to 0.95.

--
 Simon Riggs           www.2ndQuadrant.com
 PostgreSQL Training, Services and Support


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