From: Tom Lane <tgl@sss.pgh.pa.us>
To: Jeff Janes <jeff.janes@gmail.com>
cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: postgres_fdw bug in 9.6
In-reply-to: 
 <CAMkU=1y2G8VOVBHv3iXU2TMAj7-RyBFFW1uhkr5sm9LQ2=X35g@mail.gmail.com>
References: 
 <CAMkU=1y2G8VOVBHv3iXU2TMAj7-RyBFFW1uhkr5sm9LQ2=X35g@mail.gmail.com>
Comments: In-reply-to Jeff Janes <jeff.janes@gmail.com>
	message dated "Thu, 08 Dec 2016 09:07:19 -0800"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <6318.1481219450.1@sss.pgh.pa.us>
Date: Thu, 08 Dec 2016 12:50:50 -0500
Message-ID: <6319.1481219450@sss.pgh.pa.us>
Precedence: bulk
Sender: pgsql-hackers-owner@postgresql.org

Jeff Janes <jeff.janes@gmail.com> writes:
> I have a DML statement which triggers the error:
> ERROR:  XX000: outer pathkeys do not match mergeclauses
> LOCATION:  create_mergejoin_plan, createplan.c:3722

Hmm.

> Any tips on investigating this further in situ?  Or is the best option just
> to work harder on a minimal and disclosable test case?

I think we need a test case --- not minimal necessarily, but something
other people can reproduce.  You might find that setting enable_hashjoin
and/or enable_nestloop to false makes it easier to provoke the error,
since evidently this requires that we (a) generate a faulty mergejoin Path
and then (b) choose it as the cheapest one, since the error occurs while
converting it to a Plan.

BTW, if you're not doing this in a debug (--enable-cassert) build, it'd
be useful to try it in one.  I'm a little suspicious that the root cause
might be a memory-stomp type of problem, ie somebody scribbling on a
pathkey data structure without accounting for it being shared with another
path.  It's possible that cassert memory checking would help catch that.

			regards, tom lane


-- 
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers