pgsql: Implement an API to let foreign-data wrappers actually be functi

Implement an API to let foreign-data wrappers actually be functional.

This commit provides the core code and documentation needed.  A contrib
module test case will follow shortly.

Shigeru Hanada, Jan Urbanski, Heikki Linnakangas

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/bb742407947ad1cbf19355d24282380d576e7654

Modified Files
--------------
doc/src/sgml/ddl.sgml                             |   47 +++++
doc/src/sgml/fdwhandler.sgml                      |  212 +++++++++++++++++++++
doc/src/sgml/filelist.sgml                        |    1 +
doc/src/sgml/postgres.sgml                        |    1 +
doc/src/sgml/ref/create_foreign_data_wrapper.sgml |   13 +-
doc/src/sgml/ref/create_foreign_table.sgml        |    4 +-
src/backend/commands/explain.c                    |   51 ++++--
src/backend/executor/Makefile                     |    2 +-
src/backend/executor/execAmi.c                    |    5 +
src/backend/executor/execMain.c                   |    7 +
src/backend/executor/execProcnode.c               |   14 ++
src/backend/executor/nodeForeignscan.c            |  209 ++++++++++++++++++++
src/backend/foreign/foreign.c                     |  159 ++++++++++++++--
src/backend/nodes/copyfuncs.c                     |   44 +++++
src/backend/nodes/outfuncs.c                      |   41 ++++
src/backend/optimizer/README                      |    1 +
src/backend/optimizer/path/allpaths.c             |   36 ++++-
src/backend/optimizer/path/costsize.c             |   28 +++
src/backend/optimizer/plan/createplan.c           |   86 +++++++++
src/backend/optimizer/plan/planner.c              |    3 +-
src/backend/optimizer/plan/setrefs.c              |   12 ++
src/backend/optimizer/plan/subselect.c            |    4 +
src/backend/optimizer/util/pathnode.c             |   36 ++++
src/backend/optimizer/util/plancat.c              |   11 +-
src/backend/parser/analyze.c                      |   18 ++-
src/backend/rewrite/rewriteHandler.c              |    8 +-
src/backend/utils/fmgr/fmgr.c                     |   20 ++
src/include/commands/explain.h                    |   11 +
src/include/executor/nodeForeignscan.h            |   24 +++
src/include/fmgr.h                                |    1 +
src/include/foreign/fdwapi.h                      |   98 ++++++++++
src/include/foreign/foreign.h                     |    8 +
src/include/nodes/execnodes.h                     |   14 ++
src/include/nodes/nodes.h                         |    7 +-
src/include/nodes/plannodes.h                     |   12 ++
src/include/nodes/relation.h                      |   10 +
src/include/optimizer/cost.h                      |    1 +
src/include/optimizer/pathnode.h                  |    1 +
src/test/regress/expected/foreign_data.out        |    4 +-
39 files changed, 1202 insertions(+), 62 deletions(-)