On Wed, Jan 29, 2014 at 8:58 AM, Peter Geoghegan <pg@heroku.com> wrote:
I am not opposed in principle to adding new things to the counters
struct in pg_stat_statements. I just think that the fact that the overhead of installing the module on a busy production system is currently so low is of *major* value, and therefore any person that proposes to expand that struct should be required to very conclusively demonstrate that there is no appreciably increase in overhead. Having a standard deviation column would be nice, but it's still not that important. Maybe when we have portable atomic addition we can afford to be much more inclusive of that kind of thing.
Not (at this point) commenting on the details, but a big +1 on the fact that the overhead is low is a *very* important property. If the overhead starts growing it will be uninstalled - and that will make things even harder to diagnose.