| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Josh Berkus <josh(at)agliodbs(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Bruce Momjian <bruce(at)momjian(dot)us>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Default setting for autovacuum_freeze_max_age |
| Date: | 2016-10-21 17:29:42 |
| Message-ID: | CA+TgmobMuZ6Ziyw+cXEFgdXPY_6SXTysF1+vjimB2aVq_Yq52w@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Fri, Oct 21, 2016 at 1:17 PM, Josh Berkus <josh(at)agliodbs(dot)com> wrote:
> Particularly, with 9.6's freeze map, point (2) is even stronger reason
> to *lower* autovacuum_max_freeze_age. Since there's little duplicate
> work in a freeze scan, a lot of users will find that frequent freezing
> benefits them a lot ...
That's a very good point, although I hope that vacuum is mostly being
triggered by vacuum_freeze_table_age rather than
autovacuum_freeze_max_age.
On Bruce's original question, there is an answer written into our
documentation: "Vacuum also allows removal of old files from the
pg_clog subdirectory, which is why the default is a relatively low 200
million transactions."
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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