Tom Lane wrote:
> Alvaro Herrera <alvherre@commandprompt.com> writes:
> > Tom Lane wrote:
> >> Lastly, now that we have the PROC_IN_VACUUM test in GetSnapshotData,
> >> is it actually necessary for lazy vacuum to avoid setting a snapshot?
> >> It seems like it might be a good idea for it to do so in order to
> >> keep its RecentGlobalXmin reasonably current.
>
> > Hmm, I think I'd rather be inclined to get a snapshot just when it's
> > going to finish.
>
> I'm worried about keeping RecentGlobalXmin up to date during the
> vacuums, not only at the end, because it will be used for HOT page
> pruning during the vacuums.
Oh, I see. I didn't know we were doing HOT pruning during vacuum; does
it make sense?
--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.