Re: wal_buffers

On Mon, Feb 20, 2012 at 3:08 AM, Robert Haas <robertmhaas@gmail.com> wrote:
> On Sun, Feb 19, 2012 at 9:46 AM, Euler Taveira de Oliveira
> <euler@timbira.com> wrote:
>> On 19-02-2012 02:24, Robert Haas wrote:
>>> I have attached tps scatterplots.  The obvious conclusion appears to
>>> be that, with only 16MB of wal_buffers, the buffer "wraps around" with
>>> some regularity
>>>
>> Isn't it useful to print some messages on the log when we have "wrap around"?
>> In this case, we have an idea that wal_buffers needs to be increased.
>
> I was thinking about that.  I think that what might be more useful
> than a log message is a counter somewhere in shared memory.  Logging
> imposes a lot of overhead, which is exactly what we don't want here,
> and the volume might be quite high on a system that is bumping up
> against this problem.  Of course then the question is... how would we
> expose the counter value?

There is no existing statistics view suitable to include such information.
What about defining pg_stat_xlog or something?

Regards,

--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center