Message-ID: <90573804dcad67f73552898ebfe9b399875a48bd.camel@cybertec.at>
Subject: Re: pgsql: Allow insert and update tuple routing and COPY for
 foreign table
From: Laurenz Albe <laurenz.albe@cybertec.at>
To: Simon Riggs <simon@2ndquadrant.com>, Etsuro Fujita
	 <fujita.etsuro@lab.ntt.co.jp>
Cc: Robert Haas <rhaas@postgresql.org>, pgsql-committers
	 <pgsql-committers@lists.postgresql.org>, PostgreSQL Hackers
	 <pgsql-hackers@lists.postgresql.org>, ronan.dunklau@people-doc.com
Date: Wed, 24 Apr 2019 16:03:12 +0200
In-Reply-To: 
 <CANP8+jJ=8y22CqTF8x9fxnLpV3hDH_7Vpw43T4BTJWJKCxRGeA@mail.gmail.com>
References: <E1f4aif-0004qo-A6@gemulon.postgresql.org>
	 <ed0b7471dce91169d871347cf003d8094ab96895.camel@cybertec.at>
	 <5CBDB770.2060602@lab.ntt.co.jp>
	 <b459d1b1b4eb8c0d538a2c5b70e131af3c391954.camel@cybertec.at>
	 <5CC04E72.90405@lab.ntt.co.jp>
	 <CANP8+jJ=8y22CqTF8x9fxnLpV3hDH_7Vpw43T4BTJWJKCxRGeA@mail.gmail.com>
Organization: Cybertec
Content-Type: text/plain; charset="UTF-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Precedence: bulk

On Wed, 2019-04-24 at 14:25 +0100, Simon Riggs wrote:
> On Wed, 24 Apr 2019 at 12:55, Etsuro Fujita <fujita.etsuro@lab.ntt.co.jp> wrote:
>  
> > > My point is that this should not be necessary.
> > 
> > In my opinion, I think this is necessary...
> 
> Could we decide by looking at what FDWs are known to exist?
> I hope we are trying to avoid breakage in the smallest number of FDWs.

A good idea.  I don't volunteer to go through the list, but I had a look
at Multicorn, which is a FDW framework used by many FDWs, and it seems
to rely on multicornBeginForeignModify being called before
multicornExecForeignInsert (the former sets up a MulticornModifyState
used by the latter).

https://github.com/Kozea/Multicorn/blob/master/src/multicorn.c

Multicorn obviously hasn't got the message yet that the API has
changed in an incompatible fashion, so I'd argue that every
Multicorn FDW with write support is currently broken.


As Andres has argued above, it is too late to do anything more about
it than to document this and warn FDW authors as good as we can.

Yours,
Laurenz Albe