On Fri, May 24, 2013 at 11:29 AM, Robert Haas <robertmh...@gmail.com> wrote: > On Fri, May 24, 2013 at 10:53 AM, Andres Freund <and...@2ndquadrant.com> > wrote: >>> [all-visible cannot restore hint bits without FPI because of torn pages] >> >> I haven't yet thought about this sufficiently yet. I think we might have >> a chance of working around this, let me ponder a bit. > > Yeah. I too feel like there might be a solution. But I don't know > have something specific in mind, yet anyway.
One thought I had is that it might be beneficial to freeze when a page ceases to be all-visible, rather than when it becomes all-visible. Any operation that makes the page not-all-visible is going to emit an FPI anyway, so we don't have to worry about torn pages in that case. Under such a scheme, we'd have to enforce the rule that xmin and xmax are ignored for any page that is all-visible; and when a page ceases to be all-visible, we have to go back and really freeze the pre-existing tuples. I think we might be able to use the existing all_visible_cleared/new_all_visible_cleared flags to trigger this behavior, without adding anything new to WAL at all. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
