pgsql: file_fdw: Fix for generated columns

file_fdw: Fix for generated columns

Since file_fdw uses COPY internally, but COPY doesn't allow listing
generated columns in its column list, we need to make sure that we
don't add generated columns to the column lists internally generated
by file_fdw.

Reported-by: Erik Rijkers <er@xs4all.nl>

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/33215d113d61980a4b2f2aec36cdcd21fa58c1c4

Modified Files
--------------
contrib/file_fdw/file_fdw.c             |  4 ++++
contrib/file_fdw/input/file_fdw.source  |  6 ++++++
contrib/file_fdw/output/file_fdw.source | 11 +++++++++++
3 files changed, 21 insertions(+)