Re: pg_stat_activity.waiting_start

On Sat, Dec 24, 2016 at 9:56 AM, Joel Jacobson <joel(at)trustly(dot)com> wrote:
>> The difficulty with that is it'd require a gettimeofday() call for
>> every wait start. Even on platforms where those are relatively cheap,

I just realized how this can be optimized.
We only need to set wait_start for every new waiting period,
not for every wait start, i.e. not for every call to pgstat_report_wait_start():

Example:

In pgstat_report_wait_start():
if (proc->wait_start == 0)
proc->wait_start = (pg_time_t) time(NULL);

And then in pgstat_report_wait_end():
proc->wait_start = 0;

This means we only need to call time() or gettimeofday() once per
waiting period.

--
Joel Jacobson