Re: Eagerly scan all-visible pages to amortize aggressive vacuum

On Sun, Jan 26, 2025 at 3:11 PM Robert Treat <rob(at)xzilla(dot)net> wrote:
> Hmm... isn't "don't try" really more logically equivalent to "stop
> after zero failures", with "try until zero failures" more of the
> inverse... more like "never stop never stopping"?

No. Or at least, I don't think that's how English works.

> So that middle bit is trying to act as glue that pulls this all
> together. I thought the previous version was closer, with Haas's
> feedback I might go with something more like this:
>
> <para>
> - <command>VACUUM</command> normally only scans pages that have been modified
> - since the last vacuum, but
> <structfield>relfrozenxid</structfield> can only be
> - advanced when every page of the table
> - that might contain unfrozen XIDs is scanned. This happens when
> + While <command>VACUUM</command> typically scans pages that have been
> + modified since the last vacuum, it may also eagerly scan some
> all-visible but not
> + all-frozen pages in an attempt to freeze them, but the
> + <structfield>relfrozenxid</structfield> will only be advanced when
> + every page of the table that might contain unfrozen XIDs is scanned.
> + This happens when

I like that.

--
Robert Haas
EDB: http://www.enterprisedb.com