Re: Idea for getting rid of VACUUM FREEZE on cold pages

Excerpts from Russell Smith's message of mié jun 02 06:38:35 -0400 2010:

> Don't you not get a positive enough effect by adjusting the table's
> autovacuum_min_freeze_age and autovacuum_max_freeze_age. If you set
> those numbers small, it appears to me that you would get very quickly to
> a state where the vacuum would example only the most recent part of the
> table rather than the whole thing.

The problem is that vacuum doesn't know that a certain part of the table
is already frozen. It needs to scan it completely anyways. If we had a
"frozen" map, we could mark pages that are completely frozen and thus do
not need any vacuuming; but we don't (I don't recall the reasons for
this. Maybe it's just that no one has gotten around to it, or maybe
there's something else).

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Álvaro Herrera <alvherre(at)commandprompt(dot)com>
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