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: 2017-01-06T13:01:04Z
Lists: pgsql-hackers

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On 2017/01/05 12:10, Etsuro Fujita wrote:
> On 2016/12/28 17:34, Ashutosh Bapat wrote:
>> Hmm. If I understand the patch correctly, it does not return any path
>> when merge join is allowed and there are merge clauses but no hash
>> clauses. In this case we will not create a foreign join path, loosing
>> some optimization. If we remove GetExistingLocalJoinPath, which
>> returns a path in those cases as well, we have a regression in
>> performance.

> Ok, will revise, but as I mentioned upthread, I'm not sure it's a good
> idea to search the pathlist to get a merge join even in this case.  I'd
> vote for creating a merge join path from the inner/outer paths in this
> case as well.

Done.  Attached is the new version of the patch.

* I'm still not sure the search approach is the right way to go, so I 
modified CreateLocalJoinPath so that it creates a mergejoin path that 
explicitly sorts both the outer and inner relations as in 
sort_inner_and_outer, by using the information saved in that function. 
I think we could try to create a sort-free mergejoin as in 
match_unsorted_outer, but I'm not sure it's worth complicating the code.
* I modified CreateLocalJoinPath so that it handles the cheapest-total 
paths for the outer/inner relations that are parameterized if possible.
* I adjusted the code and revised some comments.

As I said upthread, we could skip costing for a local join path in 
CreateLocalJoinPath, for efficiency, but I'm not sure we should do that.

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.