On 21 January 2014 21:19, Peter Geoghegan <pg@heroku.com> wrote:
> On Tue, Jan 21, 2014 at 11:48 AM, Simon Riggs <simon@2ndquadrant.com> wrote:
>> I agree with people saying that stddev is better than nothing at all,
>> so I am inclined to commit this, in spite of the above.
>
> I could live with stddev. But we really ought to be investing in
> making pg_stat_statements work well with third-party tools. I am very
> wary of enlarging the counters structure, because it is protected by a
> spinlock. There has been no attempt to quantify that cost, nor has
> anyone even theorized that it is not likely to be appreciable.
OK, Kondo, please demonstrate benchmarks that show we have <1% impact
from this change. Otherwise we may need a config parameter to allow
the calculation.
Thanks very much.
-- Simon Riggs http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services