Re: FDW system columns

Thom Brown <thom@linux.com> writes:
> So the ctid is always 2^32-1.  Bit weird, but probably explainable.

See ItemPointerSetInvalid.

> But xmin on the file_fdw result is odd.  Why are these all over the
> place?

heap_form_tuple initializes the t_choice fields as though for a tuple
Datum, and file_fdw doesn't change it.

Just a couple hours ago I was wondering why we create system columns for
foreign tables at all.  Is there a reasonable prospect that they'll ever
be useful?  I can see potential value in tableoid, but the others seem
pretty dubious --- even if you were fetching from a remote PG server,
the XIDs would not be meaningful within our own environment.
        regards, tom lane