Re: [BUG]: the walsender does not update its IO statistics until it exits

On Wed, Feb 26, 2025 at 05:08:17AM -0500, Andres Freund wrote:
> I think it's also bad that we don't have a solution for 1), even just for
> normal connections. If a backend causes a lot of IO we might want to know
> about that long before the longrunning transaction commits.
> 
> I suspect the right design here would be to have a generalized form of the
> timeout mechanism we have for 2).
> 
> For that we'd need to make sure that pgstat_report_stat() can be safely called
> inside a transaction.  The second part would be to redesign the
> IdleStatsUpdateTimeoutPending mechanism so it is triggered independent of
> idleness, without introducing unacceptable overhead - I think that's doable.

Agreed that something in the lines of non-transaction update of the
entries could be adapted in some cases, so +1 for the idea.  I suspect
that there would be cases where a single stats kind should be able to
handle both transactional and non-transactional flush cases.
Splitting that across two stats kinds would lead to a lot of
duplication.
--
Michael