Re: Remaining VACUUM patches

Alvaro Herrera <alvherre@commandprompt.com> writes:
> The other patch was ITAGAKI Takahiro's patch to fix n_dead_tuples in
> pgstats after VACUUM when there is concurrent update activity.  This
> patch is still on hold largely because the above patch would cause it to
> be a bit obsolete.

I objected (and still object) to this patch because it allows
n_dead_tuples to drift arbitrarily far away from reality --- a series of
vacuums will incrementally update it using probably-inaccurate deltas,
and there's nothing to ensure that the result converges rather than
diverging.  In the real world it will result in n_dead_tuples becoming
less accurate, not more so.

There was some discussion about better ways to do it, IIRC, but no new
patch has been submitted.
        regards, tom lane