Re: Improvement of procArray.xmin for VACUUM

On Fri, 2007-03-23 at 17:35 -0400, Tom Lane wrote:
> To make intra-transaction advancing of xmin possible, we'd need to
> explicitly track all of the backend's live snapshots, probably by
> introducing a "snapshot cache" manager that gives out tracked
> refcounts
> as we do for some other structures like catcache entries.  This might
> have some other advantages (I think most of the current CopySnapshot
> operations could be replaced by refcount increments)

Seems like we should do this for many reasons, whether or not this is
one of them. I seem to have butted heads and lost more than once with
not being able to tell which Snapshots exist.

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