pgsql: Directly modify foreign tables.

Directly modify foreign tables.

postgres_fdw can now sent an UPDATE or DELETE statement directly to
the foreign server in simple cases, rather than sending a SELECT FOR
UPDATE statement and then updating or deleting rows one-by-one.

Etsuro Fujita, reviewed by Rushabh Lathia, Shigeru Hanada, Kyotaro
Horiguchi, Albe Laurenz, Thom Brown, and me.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/0bf3ae88af330496517722e391e7c975e6bad219

Modified Files
--------------
contrib/postgres_fdw/deparse.c                 | 100 ++++
contrib/postgres_fdw/expected/postgres_fdw.out | 314 ++++++++++--
contrib/postgres_fdw/postgres_fdw.c            | 683 ++++++++++++++++++++++---
contrib/postgres_fdw/postgres_fdw.h            |  14 +
contrib/postgres_fdw/sql/postgres_fdw.sql      | 105 +++-
doc/src/sgml/fdwhandler.sgml                   | 180 ++++++-
doc/src/sgml/postgres-fdw.sgml                 |   9 +
src/backend/commands/explain.c                 |  55 +-
src/backend/executor/execMain.c                |   1 +
src/backend/executor/nodeForeignscan.c         |  17 +-
src/backend/executor/nodeModifyTable.c         |  60 ++-
src/backend/nodes/copyfuncs.c                  |   2 +
src/backend/nodes/outfuncs.c                   |   2 +
src/backend/nodes/readfuncs.c                  |   1 +
src/backend/optimizer/plan/createplan.c        |  21 +
src/backend/optimizer/util/plancat.c           |  47 ++
src/include/foreign/fdwapi.h                   |  20 +
src/include/nodes/execnodes.h                  |   2 +
src/include/nodes/pg_list.h                    |   3 +
src/include/nodes/plannodes.h                  |   2 +
src/include/optimizer/plancat.h                |   2 +
21 files changed, 1515 insertions(+), 125 deletions(-)