Re: vacuum_freeze_table_age for 9.3.2

From: Giuseppe Broccolo <giuseppe(dot)broccolo(at)2ndquadrant(dot)it>
To: pgsql-general(at)postgresql(dot)org
Subject: Re: vacuum_freeze_table_age for 9.3.2
Date: 2013-12-05 17:29:25
Message-ID: 52A0B7F5.9000405@2ndquadrant.it
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Il 05/12/2013 17:16, Andy Colson ha scritto:
> The docs say vacuum, but the param is vacuum_freeze_table_age, so
> do I need to "vacuum freeze" all the tables, or is vacuum enough?
>
> Also, will "set vacuum_freeze_table_age = 0; vacuum freeze;" work,
> or do I need to modify the postgresql.conf and reload?

Setting vacuum_freeze_table_age to 0 forces VACUUM to always scan all
pages, effectively ignoring the visibility map. In this way a scan of
the whole table is done, ensuring all old XIDs are replaced by FrozenXID.

vacuum_freeze_table_age is a parameter with context 'user', meaning
that you can set it during a session and run a "vacuum freeze" with
the modified setting.

Giuseppe.
- --
Giuseppe Broccolo - 2ndQuadrant Italy
PostgreSQL Training, Services and Support
giuseppe(dot)broccolo(at)2ndQuadrant(dot)it | www.2ndQuadrant.it
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