Re: [HACKERS] postgres_fdw bug in 9.6

On 2017/04/08 3:33, Robert Haas wrote:
> On Mon, Apr 3, 2017 at 2:12 AM, Etsuro Fujita
> <fujita.etsuro@lab.ntt.co.jp> wrote:
>> On 2017/04/01 1:32, Jeff Janes wrote:
>>> On Thu, Mar 23, 2017 at 5:20 AM, Etsuro Fujita
>>> <fujita.etsuro@lab.ntt.co.jp <mailto:fujita.etsuro@lab.ntt.co.jp>> wrote:
>>>     Done.  Attached is a new version of the patch.
>>> Is the fix for 9.6.3 going to be just a back port of this, or will it
>>> look different?
>>
>> +1 for backporting; although that requires that GetForeignJoinPaths be
>> updated so that the FDW uses a new function to create an alternative local
>> join path (ie, CreateLocalJoinPath), that would make maintenance of the code
>> easy.
>
> Well, the problem here is that this breaks ABI compatibility.  If we
> applied this to 9.6, and somebody tried to use a previously-compiled
> FDW .so against a new server version, it would fail after the upgrade,
> because the new server wouldn't have GetExistingLocalJoinPath and also
> possibly because of the change to the structure of JoinPathExtraData.
> Maybe there's no better alternative, and maybe nothing outside of
> postgres_fdw is using this stuff anyway, but it seems like a concern.

Yeah, but I was thinking that it'd be a good idea to add a note about 
that to the release notes, to avoid such troubles.

> Also, the CommitFest entry for this seems to be a bit sketchy.  It
> claims that Tom Lane is a co-author of this patch which, AFAICS, is
> not the case.  It is listed under Miscellaneous rather than "Bug
> Fixes", which seems like a surprising decision.  And it uses a subject
> line which is neither very clear nor the same as the (also not
> particularly helpful) subject line of the email thread.

Thanks for correcting that!

Best regards,
Etsuro Fujita