Tom Lane wrote:
> Alvaro Herrera <alvherre@commandprompt.com> writes:
> > Tom Lane wrote:
> >> nonInVacuumXmin seems useless ... perhaps a vestige of some earlier
> >> version of the computation?
>
> > Hmm, not useless at all really -- only a bug of mine. Turns out the
> > notInVacuumXmin stuff is essential, so I put it back.
>
> Uh, why?
Because it's used to determine the Xmin that our vacuum will use. If
there is a transaction whose Xmin calculation included the Xid of a
transaction running vacuum, we have gained nothing from directly
excluding said vacuum's Xid, because it will affect us anyway indirectly
via that transaction's Xmin.
--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.
