Re: Idea for getting rid of VACUUM FREEZE on cold pages

> Somebody (I think Joe or Heikki) poked a big hole in this last night at
> the Royal Oak.  Although the scheme would get rid of the need to replace
> old XIDs with FrozenXid, it does not get rid of the need to set hint
> bits before you can truncate CLOG.  So in your example of an insert-only
> table that's probably never read again, there's still a minimum of one
> update visit required on every old page.  Now that's still better than
> two update visits ... but we could manage that already, just by tweaking
> vacuum's heuristics about when to freeze vs when to set hint bits.

Yeah, someone pointed that out to me too and suggested that a freeze map 
was the better solution.  I still think there's something we can do with 
pages on the visibility map but I'll have to think about it some more.

--                                   -- Josh Berkus                                     PostgreSQL Experts Inc.
                           http://www.pgexperts.com