Re: WIP: Join push-down for foreign tables

(2011/10/24 20:40), I wrote:
> I've found some issues for this CF item, and I would need some more
> effort to solve them.  So I'll mark this item as "Returned with
> feedback", and I'll propose this idea again for next CF (2011-11).

This is the second effort for $SUBJECT.  Attached patch requires
pgsql_fdw patches[1] to be applied previously.  This patch provides:

* Changes for backend
  * Add new planner node ForeignJoinPath and related routines.  In
    current design, planner consider all of possible join combinations
    between foreign tables, similar to local joins such as nested loop,
    hash join and merge join.  And if foreign join is cheapest, planner
    produces a ForeignScan plan node for a join.  So executor is not
    modified heavily since 9.1.
  * Add new FDW callback for planning join push-down between foreign
    tables on same server.  This function is optional, and allowed to
    return NULL to tell planner that that join can't be handled by the
    FDW.
  * Add server oid to RelOptInfo.  This is useless at all for relations
    other than foreign scan and foreign join, but it would reduces
    catalog lookup during foreign scan/join planning.
  * Add enable_foreignjoin GUC parameter.  Join between foreign tables
    is considered only when this parameter is on.
* Changes for pgsql_fdw
  * Implemente PlanForeignJoin callback function.

[1]http://archives.postgresql.org/pgsql-hackers/2011-11/msg00904.php

Regards,
-- 
Shigeru Hanada