Horton

Re: Testing autovacuum wraparound (including failsafe)

Masahiko Sawada <sawada.mshk@gmail.com>

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From: Masahiko Sawada <sawada.mshk@gmail.com>
To: Peter Geoghegan <pg@bowt.ie>
Cc: Andres Freund <andres@anarazel.de>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2021-05-18T07:09:37Z
Lists: pgsql-hackers 
On Tue, May 18, 2021 at 2:46 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>
> On Tue, May 18, 2021 at 2:42 PM Peter Geoghegan <pg@bowt.ie> wrote:
> >
> > On Mon, May 17, 2021 at 10:29 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> > > +1 to fix this. Are you already working on fixing this? If not, I'll
> > > post a patch.
> >
> > I posted a patch recently (last Thursday my time). Perhaps you can review it?
>
> Oh, I missed that the patch includes that fix. I'll review the patch.
>

I've reviewed the patch. Here is one comment:

    if (vacrel->num_index_scans == 0 &&
-       vacrel->rel_pages <= FAILSAFE_MIN_PAGES)
+       vacrel->rel_pages <= FAILSAFE_EVERY_PAGES)
        return false;

Since there is the condition "vacrel->num_index_scans == 0" we could
enter the failsafe mode even if the table is less than 4GB, if we
enter lazy_check_wraparound_failsafe() after executing more than one
index scan. Whereas a vacuum on the table that is less than 4GB and
has no index never enters the failsafe mode. I think we can remove
this condition since I don't see the reason why we don't allow to
enter the failsafe mode only when the first-time index scan in the
case of such tables. What do you think?

Regards,

-- 
Masahiko Sawada
EDB:  https://www.enterprisedb.com/

Commits

  1. Fix meson installation of xid_wraparound test.

  2. Add tests for XID wraparound.

  3. Add option to specify timeout seconds to BackgroundPsql.pm.

  4. Fix wrong description of BackgroundPsql's timeout.

  5. Refactor background psql TAP functions

  6. Consider triggering VACUUM failsafe during scan.

  7. Fix autovacuum log output heap truncation issue.