> > >First we must run the query in serializable mode and replace the > > >snapshot with a synthetic one, which defines visibility at the start > > >of the desired transaction > > > > > >probably it is a good idea to take a lock on all tables involved to
> > >avoid a vacuum to be started on them when the query is running. > > Would the xmin exported by that transaction prevent vacuum from > > removing any tuples still needed for the flashback snapshot? > > Sure, and that makes the mentioned lock unnecessary. Problem is, that that transaction sets a historic snapshot at a later time, so it is not yet running when vacuum looks at "global xmin". So something else needs to hold up global xmin (see prev post). Andreas ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
