For a documentation patch should this not be back ported to all
relevant versions?

On 8/21/10, Bruce Momjian <> wrote:
> Josh Berkus wrote:
>> > On further reflection, though: since we put in the BufferAccessStrategy
>> > code, which was in 8.3, the background writer isn't *supposed* to be
>> > very much involved in writing pages that are dirtied by VACUUM.  VACUUM
>> > runs in a small ring of buffers and is supposed to have to clean its own
>> > dirt most of the time.  So it's wrong to blame this on the bgwriter not
>> > holding up its end.  Rather, what you need to be thinking about is how
>> > come vacuum seems to be making lots of pages dirty on only one of these
>> > machines.
>> This is an anti-wraparound vacuum, so it could have something to do with
>> the hint bits.  Maybe it's setting the freeze bit on every page, and
>> writing them one page at a time?  Still don't understand the call to
>> pollsys, even so, though.
> We often mention that we do vacuum freeze for anti-wraparound vacuum,
> but not for pg_clog file removal, which is the primary trigger for
> autovacuum vacuum freezing.  I have added the attached documentation
> patch for autovacuum_freeze_max_age;  back-patched to 9.0.
> --
>   Bruce Momjian  <>
>   EnterpriseDB                   
>   + It's impossible for everything to be true. +

Rob Wultsch

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