Re: postgres_fdw bug in 9.6

On Tue, Aug 29, 2017 at 5:14 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp> writes:
>> [ epqpath-for-foreignjoin-11.patch ]
>
> I started looking at this. I've not yet wrapped my head around what
> CreateLocalJoinPath() is doing, but I noted that Robert's concerns
> about ABI breakage in the back branches would not be very difficult
> to satisfy. What we'd need to do is
>
> (1) In the back-branch patch, add the new fields of JoinPathExtraData
> at the end, rather than in their more natural locations. This should
> avoid any ABI break for uses of that struct, since there's no reason
> why an FDW would be creating its own variables of that type rather
> than just using what the core code passes it.
>
> (2) In the back branches, just leave GetExistingLocalJoinPath in place
> rather than deleting it. Existing FDWs would still be subject to the
> bug until they were updated, but given how hard it is to trigger, that
> doesn't seem like a huge problem.
>
> A variant of (2) is to install a hack fix in GetExistingLocalJoinPath
> rather than leaving it unchanged. I'm not very excited about that though;
> it doesn't seem unlikely that we might introduce new bugs that way, and
> it would certainly be a distraction from getting the real fix finished.
>
> We'd definitely need to do things that way in 9.6. I'm not quite sure
> whether it's too late to adopt the clean solution in v10.

It probably is now. Are you still planning to do something about this patch?

--
Robert Haas
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