On Tue, Nov 30, 2010 at 11:59 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Robert Haas <robertmh...@gmail.com> writes: >> On Tue, Nov 30, 2010 at 11:40 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: >>> Ouch. That seems like it could shoot down all these proposals. There >>> definitely isn't any way to make VM crash-safe if there is no WAL-driven >>> mechanism for setting the bits. > >> Heikki's intent method works fine, because the WAL record only clears >> the visibility map bits on redo; it never sets them. > > Uh, no, because he also had that final WAL record that would set the > bits.
Well, as already discussed upthread, that WAL record causes some other problems, so make it Heikki's intent method, without the final WAL record that breaks things. >> We could actually allow the slave to set the visibility map bits based >> on its own xmin horizon. > > Not in a crash-safe way, which is exactly the problem here. Brilliant selective quoting. -- 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
