Simon Riggs wrote: > On Wed, 2009-10-21 at 19:37 +0300, Heikki Linnakangas wrote: > >> So, I'm quite eager to just revert all those lock_twophase_recover() >> changes, and always rely on the "grant lock to dummy proc, then >> release >> it in startup process" method. If we don't want to rely on that, >> PostPrepare_Locks is an example of how to transfer lock ownership from >> one process to another correctly. > > Yes, I realised after I wrote it that PostPrepare already does that > switch, just been busy with other stuff to switch over the code. > > I think we do need some special code because of handling whole lock > queues. i.e. if there is a backend requesting an AEL but a prepared xact > has it, the lock queue will initially be Backend->Startup and needs to > end up looking like Backend->DummyProc.
Hmm, dunno about that, but there is one problem with the "grant to dummy proc, then release in startup process" approach. What if there isn't enough shared memory available to re-acquire the lock for the dummy proc? It would be rather unfortunate to throw an error and shut down the standby, instead of promoting it to a new master. In fact, what happens if you ran out of shared memory when replaying a relation_redo_lock record? Panic? -- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
