Ühel kenal päeval, R, 2007-03-09 kell 11:29, kirjutas Heikki Linnakangas: > Is there a particular reason why CLUSTER isn't MVCC-safe? It seems to me > that it would be trivial to fix, by using SnapshotAny instead of > SnapshotNow, and not overwriting the xmin/xmax with the xid of the > cluster command. > > I feel that I must missing something, or someone would've already fixed > it a long time ago...
Probably it is not MVCC safe because the relation is swapped out from under the pg_class. That is, it can be possible , that older and newer transactions read different datafiles and so simle MVCC does not work. > Csaba, you mentioned recently > (http://archives.postgresql.org/pgsql-hackers/2007-03/msg00027.php) that > you're actually using the MVCC-violation to clean up tables during a > backup. Can you tell us a bit more about that? Would you be upset if we > shut that backdoor? > > In any case, the MVCC-violation needs to be documented. I'll send a doc > patch to pgsql-patches shortly. > -- ---------------- Hannu Krosing Database Architect Skype Technologies OÜ Akadeemia tee 21 F, Tallinn, 12618, Estonia Skype me: callto:hkrosing Get Skype for free: http://www.skype.com ---------------------------(end of broadcast)--------------------------- TIP 7: You can help support the PostgreSQL project by donating at http://www.postgresql.org/about/donate
