Josh Berkus <j...@agliodbs.com> wrote: > On 11/15/2013 05:41 AM, Heikki Linnakangas wrote: >> A fundamental problem with this is that it needs to handle isolation >> reliable, so that the assertion cannot be violated when two concurrent >> backends do things. Consider the example from the manual, which checks >> that a table has at least one row. Now, if the table has two rows to >> begin with, and in one backend you delete one row, and concurrently in >> another backend you delete the other row, and then commit both >> transactions, the assertion is violated. >> >> In other words, the assertions need to be checked in serializable mode. >> Now that we have a real serializable mode, I think that's actually >> feasible. > > Going back over this patch, I haven't seen any further discussion of the > point Heikki raises above, which seems like a bit of a showstopper. > > Heikki, did you have specific ideas on how to solve this? Right now my > mind boggles.
It works fine as long as you set default_transaction_isolation = 'serializable' and never override that. :-) Of course, it sure would be nice to have a way to prohibit overrides, but that's another issue. Otherwise it is hard to see how to make it work in a general way without a mutually exclusive lock mode on the table for the duration of any transaction which modifies the table. -- Kevin Grittner EDB: 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