Another idea Jan had today was whether we could vacuum more rows if a
long-running backend is in serializable mode, like pg_dump.


Tom Lane wrote:
> Alvaro Herrera <[EMAIL PROTECTED]> 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?
> > I noticed something however -- in calculating the OldestXmin we always
> > consider all DBs, even though there is a parameter for skipping backends
> > not in the current DB -- this is because the Xmin we store in PGPROC is
> > always computed using all backends.  The allDbs parameter only allows us
> > to skip the Xid of a transaction running elsewhere, but this is not very
> > helpful because the Xmin of transactions running in the local DB will
> > include those foreign Xids.
> Yeah, this has been recognized for some time.  However the overhead of
> calculating local and global xmins in *every* transaction start is a
> significant reason not to do it.
>                       regards, tom lane
> ---------------------------(end of broadcast)---------------------------
> TIP 1: if posting/reading through Usenet, please send an appropriate
>        subscribe-nomail command to [EMAIL PROTECTED] so that your
>        message can get through to the mailing list cleanly

  Bruce Momjian   [EMAIL PROTECTED]

  + If your life is a hard drive, Christ can be your backup. +

---------------------------(end of broadcast)---------------------------
TIP 5: don't forget to increase your free space map settings

Reply via email to