On Mon, Jan 2, 2012 at 6:41 PM, Simon Riggs <si...@2ndquadrant.com> wrote: > On Mon, Jan 2, 2012 at 6:06 PM, Noah Misch <n...@leadboat.com> wrote: >> On Mon, Jan 02, 2012 at 05:09:16PM +0000, Simon Riggs wrote: >>> Attached patch makes SnapshotNow into an MVCC snapshot, initialised at >>> the start of each scan iff SnapshotNow is passed as the scan's >>> snapshot. It's fairly brief but seems to do the trick. >> >> That's a neat trick. However, if you start a new SnapshotNow scan while one >> is >> ongoing, the primordial scan's snapshot will change mid-stream. > > Do we ever do that? (and if so, Why?!? or perhaps just Where?)
Just for the record, yes we do run multiple catalog scans in some parts of the code. So I can see how we might trigger 4 nested scans, using cache replacement while scanning, so best assume more, with no guarantee of them being neatly stacked for pop/push type access. -- Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
