From: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>
To: Laurenz Albe <laurenz.albe@cybertec.at>
To: Robert Haas <rhaas@postgresql.org>
To: pgsql-committers@lists.postgresql.org
To: pgsql-hackers@lists.postgresql.org
Subject: Re: pgsql: Allow insert and update tuple routing and COPY for foreign table
Date: Mon, 22 Apr 2019 14:51:16 +0900
Message-ID: <d76c786b-8d10-f776-527e-2997ccbe0bee@lab.ntt.co.jp> (raw)
In-Reply-To: <ed0b7471dce91169d871347cf003d8094ab96895.camel@cybertec.at>
References: <E1f4aif-0004qo-A6@gemulon.postgresql.org>
<ed0b7471dce91169d871347cf003d8094ab96895.camel@cybertec.at>
Hi,
On 2019/04/20 20:53, Laurenz Albe wrote:
> On Fri, 2018-04-06 at 23:24 +0000, Robert Haas wrote:
>> Allow insert and update tuple routing and COPY for foreign tables.
>>
>> Also enable this for postgres_fdw.
>>
>> Etsuro Fujita, based on an earlier patch by Amit Langote. The larger
>> patch series of which this is a part has been reviewed by Amit
>> Langote, David Fetter, Maksim Milyutin, Álvaro Herrera, Stephen Frost,
>> and me. Minor documentation changes to the final version by me.
>>
>> Discussion: http://postgr.es/m/29906a26-da12-8c86-4fb9-d8f88442f2b9@lab.ntt.co.jp
>
> This commit makes life hard for foreign data wrappers that support
> data modifications.
>
> If a FDW implements ExecForeignInsert, this commit automatically assumes
> that it also supports COPY FROM. It will call ExecForeignInsert without
> calling PlanForeignModify and BeginForeignModify, and a FDW that does not
> expect that will probably fail.
>
> So this commit silently turns a functioning FDW into a broken FDW.
> That is not nice. Probably not every FDW is aware of this change, and
> maybe there are FDWs that support INSERT but don't want to support COPY
> for some reason.
That seems like an oversight to me. I agree that we had better checked
that a table's FDW provides BeginForeignInsert() before proceeding with
copying into the table, as your patch teaches CopyFrom() to do.
> I propose that PostgreSQL only allows COPY FROM on a foreign table if the FDW
> implements BeginForeignInsert. The attached patch implements that.
Looks good to me, including the documentation change.
> I think this should be backpatched to v11.
Agreed.
Thanks,
Amit
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To: pgsql-committers@postgresql.org
Cc: Langote_Amit_f8@lab.ntt.co.jp, laurenz.albe@cybertec.at, rhaas@postgresql.org, pgsql-committers@lists.postgresql.org, pgsql-hackers@lists.postgresql.org
Subject: Re: pgsql: Allow insert and update tuple routing and COPY for foreign table
In-Reply-To: <d76c786b-8d10-f776-527e-2997ccbe0bee@lab.ntt.co.jp>
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