Re: SQL/MED - core functionality

Hi hackers,

Attached are revised version of SQL/MED core functionality patches.

In order to make review easier, fdw_core patch has been split into
two parts, fdw_syntax and fdw_scan.  Please apply fdw_scan onto
fdw_syntax to test whole features.

The fdw_syntax.patch includes:

1) syntax for FOREIGN TABLE and FDW HANDLER
   # RULE, DEFAULT, and column level generic option are excluded to
   # make the patch simple.  But NOT NULL constraint is included
   # because it is required to inherit a table with NOT NULL
   # constraint.
2) modified catalogs, pg_foreign_table and pg_foreign_data_wrapper
3) documentation about the syntax (maybe need enhancement, though)
4) regression tests for the syntax
5) psql and pg_dump support for foreign tables and FDWs (handler)

And the fdw_scan.patch includes:

1) FDW API definition
2) ForeignScan executor node
3) Planner hook and Executor hooks
4) EXPLAIN support (included because it would effect to FdwPlan)

Note that executing SELECT and EXPLAIN statement requires FDW with
HANDLER, such as file_fdw and pgsql_fdw.  New version of file_fdw will
be posted in another thread "SQL/MED - file_fdw" soon.

Regards,
--
Shigeru Hanada