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

Hi,

On 2016-01-28 19:09:01 +0000, Robert Haas wrote:
> Only try to push down foreign joins if the user mapping OIDs match.
>
> Previously, the foreign join pushdown infrastructure left the question
> of security entirely up to individual FDWs, but it would be easy for
> a foreign data wrapper to inadvertently open up subtle security holes
> that way. So, make it the core code's job to determine which user
> mapping OID is relevant, and don't attempt join pushdown unless it's
> the same for all relevant relations.
>
> Per a suggestion from Tom Lane. Shigeru Hanada and Ashutosh Bapat,
> reviewed by Etsuro Fujita and KaiGai Kohei, with some further
> changes by me.

I noticed that this breaks some citus regression tests in a minor
manner. Namely previously file_fdw worked without a user mapping, now it
doesn't appear to anymore.

This is easy enough to fix, and it's perfectly ok for us to fix this,
but I do wonder if that's not going to cause trouble for others.

Andres