Re: Add min and max execute statement time in pg_stat_statement

On Thu, Nov 14, 2013 at 7:11 AM, Peter Geoghegan <pg@heroku.com> wrote:
> On Wed, Oct 23, 2013 at 8:52 PM, Alvaro Herrera
> <alvherre@2ndquadrant.com> wrote:
>> Hmm, now if we had portable atomic addition, so that we could spare the
>> spinlock ...
>
> That certainly seems like an interesting possibility.
>
> I think that pg_stat_statements should be made to do this kind of
> thing by a third party tool that aggregates snapshots of deltas.
> Time-series data, including (approximate) *local* minima and maxima
> should be built from that. I think tools like KONDO-san's pg_statsinfo
> tool have an important role to play here. I would like to see it or a
> similar tool become a kind of defacto standard for consuming
> pg_stat_statements' output.
>
> At this point we are in general very much chasing diminishing returns
> by adding new things to the counters struct, particularly given that
> it's currently protected by a spinlock. And adding a histogram or
> min/max for something like execution time isn't an approach that can
> be made to work for every existing cost tracked by pg_stat_statements.
> So, taking all that into consideration, I'm afraid this patch gets a
> -1 from me.

Agreed.

Regards,

-- 
Fujii Masao