Re: postgres_fdw bug in 9.6

On Thu, Dec 8, 2016 at 12:50 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> 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.

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.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company