Re: Re: [COMMITTERS] pgsql: Only try to push down foreign joins if the user mapping OIDs mat

Etsuro Fujita <fujita.etsuro@lab.ntt.co.jp> writes:
> On 2016/03/13 4:46, Andres Freund wrote:
>> ... The difference apears to be the
>> check that's now in build_simple_rel() - there was nothing hitting the
>> user mapping code before for file_fdw.

> Exactly.

> I'm not sure it's worth complicating the code to keep that behavior, so 
> I'd vote for adding the change notice to 9.6 release notes or something 
> like that in addition to updating file-fdw.sgml.

Perhaps it would be useful for an FDW to be able to specify that user
mappings are meaningless to it?  And then bypass this check for such FDWs?

I'm not really sold on enforcing that people create meaningless user
mappings.  For one thing, they're likely to be sloppy about it, which
could lead to latent security problems if the FDW later acquires a
concept that user mappings mean something.
        regards, tom lane