On Fri, Oct 21, 2016 at 10:44:41AM -0400, Tom Lane wrote:
> Bruce Momjian <bruce@momjian.us> writes:
> > Why is autovacuum_freeze_max_age's default set to 200 million, rather
> > than something like 2 billion? It seems 2 billion is half way to
> > wrap-around and would be a better default. Right now, the default seems
> > to freeze 10x more often than it has to.
>
> Please see the archives. I do not remember the reasoning, but there
> was some, and you need to justify why it was wrong not just assert
> that you think it's silly.
I think the reasoning was to avoid checking old clog files, but with
tuple transaction status bits, e.g. HEAP_XMIN_COMMITTED, which were
added long ago, I don't remember why either. I remember asking years
ago and not getting a good answer, and giving up.
If no one can give an answer, I suggest we change the default.
-- Bruce Momjian <bruce@momjian.us> http://momjian.us EnterpriseDB
http://enterprisedb.com
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