Horton

Re: postgres_fdw bug in 9.6

Etsuro Fujita <fujita.etsuro@lab.ntt.co.jp>

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From: Etsuro Fujita <fujita.etsuro@lab.ntt.co.jp>
To: Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>
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: 2017-01-05T03:00:07Z
Lists: pgsql-hackers 
On 2016/12/27 22:03, Ashutosh Bapat wrote:

You wrote:
>>> 3. Talking about saving some CPU cycles - if a clauseless full join can be
>>> implemented only using merge join, probably that's the only path available
>>> in
>>> the list of paths for the given relation. Instead of building the same
>>> path
>>> anew, should we use the existing path like GetExistingLocalJoinPath() for
>>> that
>>> case?

I wrote:
>> Hm, that might be an idea, but my concern about that is: the existing path
>> wouldn't always be guaranteed to be unprameterized.

> Why? We retain all the parameterizations (including no
> parameterization) available in the pathlist, so if it's possible to
> create an unparameterized path, there will be one.

OK, but another concern is: in cases when we consider parameterized 
paths, it might be inefficient to search the pathlist because the 
unparameterized path might be at the rear of the lengthy pathlist.  Note 
that patameterized paths would produce fewer rows and have reduced 
transfer and hence total cost, so they would be in the more front of the 
pathlist, and the unparameterized path would be in the more rear.  (Note 
that the pathlist is kept sorted by total cost.)

Best regards,
Etsuro Fujita

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.