Re: Status of FDW pushdowns

On Thu, Nov 21, 2013 at 10:46:14AM -0500, Tom Lane wrote:
> Merlin Moncure <mmoncure(at)gmail(dot)com> writes:
> > On Thu, Nov 21, 2013 at 9:05 AM, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
> >> I know join pushdowns seem insignificant, but it helps to restrict what
> >> data must be passed back because you would only pass back joined rows.
>
> > By 'insignificant' you mean 'necessary to do any non-trivial real
> > work'. Personally, I'd prefer it if FDW was extended to allow
> > arbitrary parameterized queries like every other database connectivity
> > API ever made ever.
>
> [ shrug... ] So use dblink.

Not with a non-PostgreSQL data source.

> For better or worse, the FDW stuff is following the SQL standard's
> SQL/MED design, which does not do it like that.

What SQL/MED specifies along this line is purely a caution against
making a specification without a reference implementation. If I'm
reading it correctly, it's literally impossible to make what they
suggest safe.

Given those givens, we're free to do this in a way that's not
barking-at-the-moon crazy. At least two inter-database communication
links which work with PostgreSQL do this..

Cheers,
David.
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