From: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: postgres_fdw bug in 9.6 |
Date: | 2016-12-10 18:29:05 |
Message-ID: | CAMkU=1zEAryzjEa-njBkV2+uXXVHHk6u2V2eS1MT+zP7s=vj1Q@mail.gmail.com |
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Lists: | pgsql-hackers |
On Thu, Dec 8, 2016 at 10:28 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> > Maybe it would help for Jeff to use elog_node_display() to the nodes
> > that are causing the problem - e.g. outerpathkeys and innerpathkeys
> > and best_path->path_mergeclauses, or just best_path - at the point
> > where the error is thrown. That might give us enough information to
> > see what's broken.
>
> I'll be astonished if that's sufficient evidence. We already know that
> the problem is that the input path doesn't claim to be sorted in a way
> that would match the merge clauses, but that doesn't tell us how such
> a path came to be generated (or, if it wasn't intentionally done, where
> the data structure got clobbered later).
>
> It's possible that setting a breakpoint at create_mergejoin_path and
> capturing stack traces for all calls would yield usable insight. But
> there are likely to be lots of calls if this is an 8-way join query,
> and probably only a few are wrong.
>
> I'd much rather have a test case than try to debug this remotely.
> Bandwidth too low.
>
I didn't get an asserts on the assert-enabled build.
I have a test case where I made the fdw connect back to itself, and
stripped out all the objects that I could and still reproduce the case. It
is large, 21MB compressed, 163MB uncompressed, so I am linking it here:
https://drive.google.com/open?id=0Bzqrh1SO9FcEZkpPM0JwUEMzcmc
When running this against and default configured 9.6.1 or 10devel-a73491e,
I get the error.
psql -U postgres -f <(xzcat combined_anon.sql.xz)
...
ERROR: outer pathkeys do not match mergeclauses
STATEMENT: explain update local1 set local19 = jj_join.local19 from
jj_join where local1.local12=jj_join.local12 and local1.local12 in
('ddd','bbb','aaa','abc');
Cheers,
Jeff
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