Re: Status of FDW pushdowns

On Thu, Nov 28, 2013 at 12:54 AM, David Fetter <david@fetter.org> wrote:
> On Wed, Nov 27, 2013 at 10:29:34AM -0300, Alvaro Herrera wrote:
>> Shigeru Hanada escribió:
>>
>> > SQL/MED standard doesn't say much about PASS THROUGH mode, especially
>> > about interaction between client.  Besides it, I think it would be
>> > nice to allow arbitrary FDW as backend of dblink interface like this:
>> >
>> > postgres=> SELECT dblink_connect('con1', 'server name of an FDW');
>> > postgres=> SELECT * FROM dblink('con1', 'some query written in remote
>> > syntax') as t(/* record type definition */...);
>> >
>> > This provides a way to execute query without defining foreign table.
>>
>> Seems to me that if you want to read remote tables without creating a
>> foreign table, you could define them locally using something like the
>> WITH syntax and then use them normally in the rest of the query.
>
> WITH, or SRF, or whatever, the point is that we need to be able to
> specify what we're sending--probably single opaque strings delimited
> just as we do other strings--and what we might get back--errors only,
> rows, [sets of] refcursors are the ones I can think of offhand.

+1

The input-output formats need to be defined clearly.

How about sending parse trees? Is it even possible?

> What we can't do is assume that our parser needs to, or even could, in
> principle, understand these things in more detail than that.

Agreed.

I wonder if its possible to give this task to the FDW implementing
authority instead, and get FDW to translate to the required format.




--
Regards,

Atri
l'apprenant