Horton

Re: postgres_fdw bug in 9.6

Tom Lane <tgl@sss.pgh.pa.us>

View thread View on postgr.es
From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Jeff Janes <jeff.janes@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2016-12-08T18:28:07Z
Lists: pgsql-hackers 
Robert Haas <robertmhaas@gmail.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.

			regards, tom lane

Commits

  1. Fix test case for 'outer pathkeys do not match mergeclauses' fix.

  2. postgres_fdw: Avoid 'outer pathkeys do not match mergeclauses' error.

  3. postgres_fdw: Consider foreign joining and foreign sorting together.

  4. Allow foreign and custom joins to handle EvalPlanQual rechecks.

  5. Allow FDWs to push down quals without breaking EvalPlanQual rechecks.