Re: New vacuum option to do only freezing

On Thu, Feb 28, 2019 at 2:46 AM Bossart, Nathan <bossartn@amazon.com> wrote:
>
> On 2/27/19, 2:08 AM, "Masahiko Sawada" <sawada.mshk@gmail.com> wrote:
> >> +       if (skip_index_vacuum)
> >> +               appendStringInfo(&buf, ngettext("%.0f tuple is left as dead.\n",
> >> +                                                                               "%.0f tuples are left as dead.\n",
> >> +                                                                               nleft),
> >> +                                                nleft);
> >>
> >> I think we could emit this metric for all cases, not only when
> >> DISABLE_INDEX_CLEANUP is used.
> >
> > I think that tups_vacuumed shows total number of vacuumed tuples and
> > is already shown in the log message. The 'nleft' counts the total
> > number of recorded dead tuple but not counts tuples are removed during
> > HOT-pruning. Is this a valuable for users in non-DISABLE_INDEX_CLEANUP
> > case?
>
> I think it is valuable.  When DISABLE_INDEX_CLEANUP is not used or it
> is used for a relation with no indexes, it makes it clear that no
> tuples were left marked as dead.  Also, it looks like all of the other
> information here is provided regardless of the options used.  IMO it
> is good to list all of the stats so that users have the full picture
> of what VACUUM did.
>

I see your point. That seems good to me.

Attached the updated version patch. I've incorporated all review
comments I got and have changed the number of tuples being reported as
'removed tuples'. With this option, tuples completely being removed is
only tuples marked as unused during HOT-pruning, other dead tuples are
left. So we count those tuples during HOT-pruning and reports it as
removed tuples.

Regards,

--
Masahiko Sawada
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center