Re: Page at a time index scan

On Wed, 2006-05-03 at 13:39 -0400, Tom Lane wrote:
> Simon Riggs <simon@2ndquadrant.com> writes:
> > So do you see a problem scenario like this?
>
> > A, B and C separate backends:
> > A1 Reads page, some row versions are *not* marked LP_DELETE but will be
> > later when A2 happens
> >     B1 VACUUM removes dead rows, just happens to be all of them
> >     B2 Recycles page into FSM
> >         C1 Inserts new data into old page
> > A2 Attempts to update old page to notify about dead rows (UGH!)
>
> Can't happen; a page cannot be recycled until all concurrent
> transactions are gone.  In any case, the LP_DELETE marking code will
> certainly take care to check that the entries it's trying to mark
> are still the same ones it meant to mark.

!

So do you see a problem with page deletion, or not? If so, what is it?

This patch looks good to me, based upon everything said.

--
  Simon Riggs
  EnterpriseDB   http://www.enterprisedb.com