What is the extent of FDW join pushdown support in 9.5?

The 9.5 release notes contain this promising but cryptic item:

- Allow foreign data wrappers and custom scans to implement join
pushdown (KaiGai Kohei)

As phrased, this seems to mean, "it can be done, but we haven't done
it". But there is no link to any documentation that explains how to do
this. The commit that appears to have added this feature touches
postgres_fdw, but neither the documentation nor the tests show anything
about this feature, and I haven't been able to reproduce anything that
would seem to indicate anything like this is at work.

So what is the actual extent of this feature?

It says these enhancement on interface allows extensions to implement
join operation in their own way (including remote join in case of FDW),
however, enhancement of postgres_fdw is not yet upstreamed.

So, how about the description below? It focuses on interface enhancement.

- Allow extensions to implement join in their own way using foreign
data wrappers and customer scan interface.

Thanks,
--
NEC Business Creation Division / PG-Strom Project
KaiGai Kohei <kaigai@ak.jp.nec.com>

--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers

On 9/15/15 10:02 PM, Kouhei Kaigai wrote:

The 9.5 release notes contain this promising but cryptic item:

- Allow foreign data wrappers and custom scans to implement join
pushdown (KaiGai Kohei)

As phrased, this seems to mean, "it can be done, but we haven't done
it". But there is no link to any documentation that explains how to do
this. The commit that appears to have added this feature touches
postgres_fdw, but neither the documentation nor the tests show anything
about this feature, and I haven't been able to reproduce anything that
would seem to indicate anything like this is at work.

So what is the actual extent of this feature?

It says these enhancement on interface allows extensions to implement
join operation in their own way (including remote join in case of FDW),
however, enhancement of postgres_fdw is not yet upstreamed.

Thank you for this clarification. I suppose this item is correct as
written.

--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers

On Wed, Sep 16, 2015 at 04:32:51PM -0400, Peter Eisentraut wrote:

On 9/15/15 10:02 PM, Kouhei Kaigai wrote:

The 9.5 release notes contain this promising but cryptic item:

- Allow foreign data wrappers and custom scans to implement join
pushdown (KaiGai Kohei)

As phrased, this seems to mean, "it can be done, but we haven't done
it". But there is no link to any documentation that explains how to do
this. The commit that appears to have added this feature touches
postgres_fdw, but neither the documentation nor the tests show anything
about this feature, and I haven't been able to reproduce anything that
would seem to indicate anything like this is at work.

So what is the actual extent of this feature?

It says these enhancement on interface allows extensions to implement
join operation in their own way (including remote join in case of FDW),
however, enhancement of postgres_fdw is not yet upstreamed.

Thank you for this clarification. I suppose this item is correct as
written.

Yes, it was cryptically written on purpose. ;-)

--
Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ As you are, so once was I. As I am, so you will be. +
+ Roman grave inscription                             +

--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers