Subject: Re: BUG #15552: Unexpected error in COPY to a foreign table in a
 transaction
References: <15552-c64aa14c5c22f63c@postgresql.org>
 <8e82d10d-cc16-eed4-7634-3654f59d8053@lab.ntt.co.jp>
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 <5C18ECBB.2000507@lab.ntt.co.jp>
 <LEJPR01MB001074FD67CB65B539122E4DE7BD0@LEJPR01MB0010.DEUPRD01.PROD.OUTLOOK.DE>
 <3539e73a-313a-5406-27c7-850affb47921@lab.ntt.co.jp>
 <20181219023814.GA6577@paquier.xyz>
From: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>
Message-ID: <6daa6d4a-d4a9-bd2c-0b84-c4e31d2b9844@lab.ntt.co.jp>
Date: Wed, 19 Dec 2018 11:52:09 +0900
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To: Michael Paquier <michael@paquier.xyz>
Cc: Luis Carril <luis.carril@swarm64.com>,
        Etsuro Fujita <fujita.etsuro@lab.ntt.co.jp>,
        "pgsql-bugs@lists.postgresql.org" <pgsql-bugs@lists.postgresql.org>,
        PG Bug reporting form <noreply@postgresql.org>,
        Michael Paquier <michael.paquier@gmail.com>
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On 2018/12/19 11:38, Michael Paquier wrote:
> On Wed, Dec 19, 2018 at 10:19:58AM +0900, Amit Langote wrote:
>> Not sure that's a good name to give to the test file, although since I'm
>> not greatly enthusiastic about adding a TAP test for this, I don't have a
>> good suggestion.  Maybe, choose a more generic name?  Michael, any
>> suggestions?
> 
> I have looked at the proposal seriously myself, and adding a TAP test
> for that edge case is overdoing it.  So why not just adding a test to
> postgres_fdw.sql?  The failure can be triggered with installcheck and
> wal_level =3D minimal.  Not everybody tests with non-default options, but
> some of us do.

Yeah, I said that upthread.

> Attached is a more simple, updated, patch which adds a new test and a
> comment.  I would rather not play with the semantics of heap_sync() on
> the back branches as well as on a thread dealing with a bug about COPY
> with foreign tables.  Such discussions deserve a larger audience on
> -hackers.

+1

Patch looks good, by the way.

> it is a bit funny to see COPY FREEZE working for foreign tables
> actually, but perhaps this has some use-cases for some FDWs, so I'd
> rather not touch it.

Hmm, note that we don't pass CopyState->freeze option to the FDW drivers
today, though we may in the future when we add an *actual* COPY interface
to FDWs.  Wouldn't it be a good idea to prevent specifying the FREEZE
option for foreign tables as COPY targets until then?  Of course, that's
something for -hackers to consider.

Thanks,
Amit