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
Date: Thu, 08 Dec 2016 12:50:50 -0500
Message-ID: <6319.1481219450@sss.pgh.pa.us> (raw)
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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
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, jeff.janes@gmail.com
Subject: Re: postgres_fdw bug in 9.6
In-Reply-To: <6319.1481219450@sss.pgh.pa.us>
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