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

On Mon, Mar 14, 2016 at 1:05 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
>> On Sun, Mar 13, 2016 at 10:51 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>>> 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.
>
>> I think we should just fix build_simple_rel() so that it doesn't fail
>> if there is no user mapping.  It can just set rel->umid to InvalidOid
>> in that case, and if necessary we can adjust the code elsewhere to
>> tolerate that.  This wasn't an intentional behavior change, and I
>> think we should just put things back to the way they were.
>
> So, allow rel->umid to be InvalidOid if there's no user mapping, and
> when dealing with a join, allow combining when both sides have InvalidOid?

Exactly.  And we should make sure (possibly with a regression test)
that postgres_fdw handles that case correctly - i.e. with the right
error.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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