Excerpts from Heikki Linnakangas's message of mié feb 29 16:29:26 -0300 2012: > On 29.02.2012 21:18, Alvaro Herrera wrote: > > Excerpts from Heikki Linnakangas's message of mié feb 29 16:09:02 -0300 > > 2012: > >> I thought my view on how this should be done was already clear, but just > >> in case it isn't, let me restate: Enlarge the page header to make room > >> for the checksum. To handle upgrades, put code in the backend to change > >> the page format from old version to new one on-the-fly, as pages are > >> read in. Because we're making the header larger, we need to ensure that > >> there's room on every page. To do that, write a utility that you run on > >> the cluster before running pg_upgrade, which moves tuples to ensure > >> that. To ensure that the space doesn't get used again before upgrading, > >> change the old version so that it reserves those N bytes in all new > >> insertions and updates (I believe that approach has been discussed > >> before and everyone is comfortable with backpatching such a change). All > >> of this in 9.3. > > > > Note that if we want such an utility to walk and transform pages, we > > probably need a marker in the catalogs somewhere so that pg_upgrade can > > make sure that it was done in all candidate tables -- which is something > > that we should get in 9.2 so that it can be used in 9.3. > > In the simplest form, the utility could just create a magic file in the > data directory to indicate that it has run. All we need is a boolean > flag, unless you want to be fancy and make the utility restartable. > Implemented that way, there's no need to have anything in the catalogs.
Well, I find it likely that people with huge and/or high velocity databases would want to get fancy about it, so that they can schedule it as they see fit. What I wouldn't like is an utility that is optional, so that we end up with situations after upgrade that do have the new page format, others that don't. -- Álvaro Herrera <alvhe...@commandprompt.com> The PostgreSQL Company - Command Prompt, Inc. PostgreSQL Replication, Consulting, Custom Development, 24x7 support -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
