Re: Improvement of procArray.xmin for VACUUM

Gregory Stark <stark@enterprisedb.com> writes:
> Well I think this would be the same infrastructure we would need to do
> the other discussed improvement to address pg_dump's impact. That
> would require us to publish the youngest xmax of the live
> snapshots. Vacuum could deduce that that xid cannot possibly see any
> transactions between the youngest extant xmax and the oldest
> in-progress transaction.

... and do what with the knowledge?  Not remove tuples, because any such
tuples would be part of RECENTLY_DEAD update chains that that xact might
be following now or in the future.

            regards, tom lane