Re: Background Processes and reporting

Hi,

On 2016-03-11 11:16:32 -0800, Andres Freund wrote:
> It seems rather worthwhile to think about how we can expand the coverage
> of progress tracking to other types of background processes.

WRT the progress reporting patch, I think we should split (as afaics was
discussed in the thread for a while) off the new part of PgBackendStatus
into it's own structure.

That'd not just allow using this from non-backend processes, but would
also have the advantage that the normal PgBackendStatus' changecount
doesn't advance quite so rapidly. E.g. when reporting progress of a
vacuum, the changecount will probably change at quite a rapid rate, but
that's uninteresting for e.g. pg_stat_activity.

> Similarly for the wait event stuff - checkpointer, wal writer,
> background writer are in many cases processes that very often are
> blocked on locks, IO and such. Thus restricting the facility to
> database connected processes seems like a loss.

I think one way to address this would be to not only report
PgBackendStatus type processes in pg_stat_activity. While that'd
obviously be a compatibility break, I think it'd be an improvement.

Regards,

Andres