Re: Improve description of XLOG_RUNNING_XACTS

At Thu, 21 Jul 2022 16:58:45 +0900, Masahiko Sawada  wrote in 
> > > The patch looks good to me.

By the way +1 to this.

> > The subxids can reach TOTAL_MAX_CACHED_SUBXIDS =
> > PGPROC_MAX_CACHED_SUBXIDS(=64) * PROCARRAY_MAXPROCS. xact_desc_commit
> > also shows subtransactions but they are at maximum 64.  I feel like
> > -0.3 if there's no obvious advantage showing them.
> 
> xxx_desc() functions are debugging purpose functions as they are used
> by pg_waldump and pg_walinspect etc. I think such functions should
> show all contents unless there is reason to hide them. Particularly,
> standby_desc_running_xacts() currently shows subtransaction
> information only when subtransactions are overflowed, which got me
> confused when inspecting WAL records.

I'm not sure just confusing can justify that but after finding
logicalmsg_desc dumps the whole content, I no longer feel against to
show subxacts.  

Just for information, but as far as I saw, relmap_desc shows only the
length of "data" but doesn't dump all of it. generic_desc behaves the
same way.  Thus we could just show "%d subxacts" instead of dumping
out the all subxact ids just to avoid that confusion.

However, again, I no longer object to show all subxids.

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center