On Sun, Apr 29, 2012 at 1:40 PM, Kevin Grittner <kevin.gritt...@wicourts.gov> wrote:
>> IMHO the desired behaviour would be >> >> * prevent default_transaction_isolation = serializable as a default >> setting when we enter Hot Standby by throwing a FATAL error from >> the startup process. I can help implement that if we agree. > > I'm not sure how well that plays for all users of HS. It would work > for us because there are a number of settings we want to change on a > HS; we use a different postgresql.conf from the master, so this works > fine. I am concerned about people who want to promote the HS to a > new master without swapping in a different conf file and doing a > reload or restart -- if they want serializable transactions as the > default on their master, how would this work? I can see you might want to have a standby with hot_standby=off that was immediately ready to take the place of the master. In that case, the setting of default_transaction_isolation would have no effect on the standby, so you are ready and waiting. If you request hot_standby=on presumably you're not going to want a continuous stream of ERRORs. Blocking that completely is hard because we would need to test the parameter file as well as testing user or database settings. The only way default_transaction_isolation = serializable would be acceptable when hot_standby = on is if we silently downgrade the isolation level to read committed. That way everything just works, albeit not quite as requested. So I think that's the best way forwards. -- Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
