| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Thom Brown <thom(at)linux(dot)com> |
| Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: FDW system columns |
| Date: | 2011-11-13 00:38:10 |
| Message-ID: | 22453.1321144690@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Thom Brown <thom(at)linux(dot)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
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