Date: Mon, 9 Dec 2019 12:18:44 -0500
From: Bruce Momjian <bruce@momjian.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Thomas Munro <thomas.munro@gmail.com>,
	Kyotaro Horiguchi <horikyota.ntt@gmail.com>,
	pgsql-hackers <pgsql-hackers@postgresql.org>,
	Stephen Frost <sfrost@snowman.net>
Subject: Re: Append with naive multiplexing of FDWs
Message-ID: <20191209171844.GA5192@momjian.us>
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On Thu, Dec  5, 2019 at 03:19:50PM -0500, Robert Haas wrote:
> On Thu, Dec 5, 2019 at 1:12 PM Bruce Momjian <bruce@momjian.us> wrote:
> > I agree with Stephen's request.  We have been waiting for the executor
> > rewrite for a while, so let's just do something simple and see how it
> > performs.
> 
> I'm sympathetic to the frustration here, and I think it would be great
> if we could find a way forward that doesn't involve waiting for a full
> rewrite of the executor.  However, I seem to remember that when we
> tested the various patches that various people had written for this
> feature (I wrote one, too) they all had a noticeable performance
> penalty in the case of a plain old Append that involved no FDWs and
> nothing asynchronous. I don't think it's OK to have, say, a 2%
> regression on every query that involves an Append, because especially
> now that we have partitioning, that's a lot of queries.
> 
> I don't know whether this patch has that kind of problem. If it
> doesn't, I would consider that a promising sign.

Certainly any overhead on normal queries would be unacceptable.

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

+ As you are, so once was I.  As I am, so you will be. +
+                      Ancient Roman grave inscription +