Horton

Re: Explain buffers wrong counter with parallel plans

Alvaro Herrera <alvherre@2ndquadrant.com>

View thread View on postgr.es
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Robert Haas <robertmhaas@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Adrien Nayrat <adrien.nayrat@anayrat.info>, Andres Freund <andres@anarazel.de>, PostgreSQL mailing lists <pgsql-hackers@postgresql.org>
Date: 2018-06-29T22:38:36Z
Lists: pgsql-hackers 
On 2018-Jun-29, Tom Lane wrote:

> Alvaro Herrera <alvherre@2ndquadrant.com> writes:
> > I'm CCing Tom here, as author of the patch that caused (most of) the
> > issue.
> 
> Uh ... me?  I thought this was a parallel-query issue, which I've
> pretty much not been involved in.

Well, maybe it's a matter of opinion.  Amit K said a few messages back
that your 01edb5c7fc3b ("Improve division of labor between
execParallel.c and nodeGather[Merge].c.") had changed the way these
numbers are printed, but only now I realize that he then indicated that
a different code path was already behaving in that way.

I stand by my opinion that we should not give misleading/confusing info;
either let's show it all in the default output, or only do it in
VERBOSE, but if the latter then let's suppress the misleading numbers in
the default output.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Commits

  1. Adjust comment atop ExecShutdownNode.

  2. Prohibit shutting down resources if there is a possibility of back up.

  3. Fix buffer usage stats for parallel nodes.

  4. Match the buffer usage tracking for leader and worker backends.

  5. Improve division of labor between execParallel.c and nodeGather[Merge].c.