Jeff Davis wrote: > On Tue, 2010-03-16 at 15:29 +0000, Greg Stark wrote: > > I'm picturing storing a bit in the visibility map indicating that *no* > > records are visible in a given page. > > I've been thinking for a while that we could store the visibility > information in a structure separate from the heap -- sort of like the > visibility map, but per-tuple and authoritative rather than a per-page > hint. > > There are all kinds of challenges there, but it might be worth thinking > about. Visibility information is highly compressible, and requires > constant maintenance (updates, deletes, freezing, etc.). It also might > make it possible to move to 64-bit xids, if we wanted to.
I don't think we want to move to 64-bit xids becasue we would still need to do vacuum freeze to trim the clog. In fact we do vacuum freeze much more frequently than required for 32-bit xids for this very reason. -- Bruce Momjian <[email protected]> http://momjian.us EnterpriseDB http://enterprisedb.com PG East: http://www.enterprisedb.com/community/nav-pg-east-2010.do -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
