Re: Statistics updates is delayed when using `commit and chain`

Andres Freund <andres(at)anarazel(dot)de> writes:
> On 2022-08-01 12:43:23 -0400, Tom Lane wrote:
>> Yeah. I think we'd need to get rid of the "bool force" argument
>> of pgstat_report_stat, and instead have it manage things internally
>> based on understanding whether the current process uses a reporting
>> timeout timer or not (if not, always send the report right away).

> It's not as simple as looking at the backend type, I think. We'd not want to
> enable a timer in the commit-and-chain context, even in a normal backend -
> there's no chance we'll go idle.

No, but that's not the point. During CommitTransaction we should check
to see if it's more than X amount of time since our last stats report,
and if so send a new one. No timer interaction involved there. When
we go idle, if not inside a transaction and a report needs to be sent,
then compute the wait time till it should be sent and set a timer for
that.

> I wonder if it was the wrong call to use timers for IdleSessionTimeout,
> IdleInTransactionSessionTimeout and pgstats. We always use nonblocking socket
> IO these days, so perhaps we should instead just compute a relevant timeout
> for the WaitEventSetWait() call?

Meh. I think that that would end up with duplicative logic and
duplicative gettimeofday calls, unless your idea is to get rid of
the timeout.c facilities altogether.

regards, tom lane