On Fri, 2008-03-14 at 08:43 -0700, Steve Crawford wrote: > > Also, it is MVCC-safe only from 8.3 upwards; on older versions > > it (incorrectly) deletes dead tuples that are still visible to old > > transactions. > > > > > More interesting. I may have a broken mental-model. I *thought* that > CLUSTER acquired exclusive locks and that acquisition of the exclusive > lock would imply that there couldn't be any transactions accessing that > table. Where is my misunderstanding?
Here's a scenario: - transaction A starts to read table A; - transaction B starts, deletes some records from table B, end ends; - transaction C starts and clusters table B; - transaction A finished reading table A, and now tries to read the records just deleted by transaction B; Question: under MVCC rules should transaction A see the deleted records or not ? Unfortunately I don't know for sure the answer, but if it is yes, then bad luck for transaction A, because cluster just ate them. And the locking will not help this... Cheers, Csaba. -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
