On Fri, 2010-03-19 at 01:59 +0530, Gokulakannan Somasundaram wrote: > > The visibility map itself is already an example of > compression. If > visibility information were randomly distributed among tuples, > the > visibility map would be nearly useless. > > > I believe it is very difficult to make visibility map update friendly > without compromising durability. But such a functionality is very > much wanted in PG still.
Surely the VM is already update-friendly. If you update a tuple in a page with the visibility bit set, the bit must be unset or you will get wrong results. Regards, Jeff Davis -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers