Tom Lane wrote:
> Bruce Momjian <> writes:
> > 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.
> This patch does not actually seem like an improvement.  The paragraph is
> all about transaction age, but you've inserted something entirely
> unrelated, and not only that but chosen to make the unrelated thing seem
> like the major consequence and anti-wraparound an afterthought.

Well, the reason that value is 200 million is for pg_clog cleanup, not
for xid wraparound protection.  The next sentence does relate to xid
wraparound, but it seems to fit because the previous sentence ends with
xid wraparound:

        Note that the system will launch autovacuum processes to
        prevent wraparound even when autovacuum is otherwise disabled.

If we were worried about just xid wraparound I assume the value would be
2 billion.

Do you have a suggestion?  Reorder the items?

  Bruce Momjian  <>

  + It's impossible for everything to be true. +

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