Re: [HACKERS] postgres_fdw bug in 9.6

From: Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, David Steele <david(at)pgmasters(dot)net>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [HACKERS] postgres_fdw bug in 9.6
Date: 2018-01-19 06:53:12
Message-ID: 5A6195D8.8060206@lab.ntt.co.jp
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(2018/01/18 15:40), Etsuro Fujita wrote:
> (2018/01/18 7:09), Robert Haas wrote:
>> On Wed, Jan 17, 2018 at 4:08 PM, Tom Lane<tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>> It's debatable perhaps -- I tend to err in the other direction.
>>> But likewise, I don't care deeply. Just push it ...
>>
>> Done.

I noticed that this test case added by the patch is not appropriate:

+-- multi-way join involving multiple merge joins
+EXPLAIN (VERBOSE, COSTS OFF)
+SELECT * FROM ft1, ft2, ft4, ft5 WHERE ft1.c1 = ft2.c1 AND ft1.c1 = ft4.c1
+ AND ft1.c1 = ft5.c1 FOR UPDATE;
+SELECT * FROM ft1, ft2, ft4, ft5 WHERE ft1.c1 = ft2.c1 AND ft1.c1 = ft4.c1
+ AND ft1.c1 = ft5.c1 FOR UPDATE;

because it doesn't inject extra Sort nodes into EPQ recheck plans, so it
works well without the fix. I modified this to inject a Sort into the
recheck plan of the very first foreign join. Attached is a patch for that.

Best regards,
Etsuro Fujita

Attachment Content-Type Size
postgres-fdw-regress.patch text/x-diff 20.8 KB

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