Horton

Re: postgres_fdw bug in 9.6

Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>

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From: Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>
To: Etsuro Fujita <fujita.etsuro@lab.ntt.co.jp>
Cc: Jeff Janes <jeff.janes@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Robert Haas <robertmhaas@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2017-01-10T12:15:22Z
Lists: pgsql-hackers 
>
>> If the inner and/or outer paths are not ordered as required, we will need
>> to
>> order them. Code below doesn't seem to handle that case.
>>                     /*
>>                      * If the paths are already well enough ordered, we
>> can
>>                      * skip doing an explicit sort.
>>                      */
>>                     if (outerkeys &&
>>                         pathkeys_contained_in(outerkeys,
>> outer_path->pathkeys))
>>                         outerkeys = NIL;
>>                     if (innerkeys &&
>>                         pathkeys_contained_in(innerkeys,
>> inner_path->pathkeys))
>>                         innerkeys = NIL;
>
>
> I might be missing something, but if the outer/inner paths are already well
> sorted, we wouldn't need an explicit sort, so we can set the
> outerkeys/innerkeys to NIL safely.  (You can find the same optimization in
> try_mergejoin_path.)

Actually I didn't notice that create_mergejoin_path saves those keys
in the MergePath and then adds sorting steps during planning. Sorry
for the trouble.

Another concern here is that we are copying pieces of logic in
add_paths_to_joinrel() without arranging it as neatly as in that
function.

-- 
Best Wishes,
Ashutosh Bapat
EnterpriseDB Corporation
The Postgres Database Company

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.