Re: 9.5 release notes may need ON CONFLICT DO NOTHING compatibility notice for FDW authors

On Sun, May 24, 2015 at 4:22 PM, Peter Geoghegan <pg(at)heroku(dot)com> wrote:
> As things stand, every other possible ON CONFLICT clause will throw an
> error in some way before the FDW is consulted at all, so FDW authors
> need not concern themselves with those other cases (unless perhaps we
> allow ON CONFLICT DO UPDATE to not require an inference specification
> in a last minute behavioral tweak, as suggested by Simon Riggs, making
> ON CONFLICT DO UPDATE support by foreign data wrappers a possibility
> that must be considered).

AddForeignUpdateTargets() actually won't be called with ON CONFLICT DO
UPDATE, and so it isn't exactly true that the only obstacle to making
FDWs support ON CONFLICT DO UPDATE is around inference of arbiter
unique indexes on the foreign side. It's *almost* true, though.

--
Peter Geoghegan