Re: Re: [COMMITTERS] pgsql: Use LEFT JOINs in some system views in case referenced row doesn

Michael Paquier <michael(dot)paquier(at)gmail(dot)com> writes:
> On Sun, Sep 11, 2016 at 5:21 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> The fact that the pg_stat_replication view does show walsender processes
>> seems like possibly a reasonable argument for not showing them in
>> pg_stat_activity. But we'd have to do some rejiggering of the view
>> definition to make that happen.

> We may actually had better show WAL sender processes in
> pg_stat_activity. An argument in favor of that is the tracking of
> WaitEventSet events (or latches if you want).

Also, walsenders count against MaxBackends don't they? So not showing
them could contribute to confusion about why an installation is hitting
the connection limit.

If we do keep them in the view, I would definitely vote for having them
set their "query" fields to something that shows they're walsenders.
It's awfully late to be doing anything complicated there for 9.6,
but we could just set the query to "walsender" and plan to improve
on that in future releases.

regards, tom lane