Jim Fulton wrote at 2004-7-15 17:18 -0400:
Dieter Maurer wrote: I don't think anyone find versions useful in cases where locks matter. With versions, if you get resource contention, someone loses.
Yes, but hopefully the short running (inexpensive) and not the long running (expensive) process...
Long-running subtransactions as I'm proposing would rely on mult-version concurrency control, rather than locks.
MVCC is nice (we already use it) but its help for write contention is limited. The locks used by the current "Version"s are better suited for long running transactions.
In either case, if you have resource contention, you are probably out of luck.
Luck is not a binary concept ;-) Our current most essential use case for "Version"s is reindexing large catalogs. Reindexing can take hours. It is bad when the reindexing fails due to a write conflict. It is much more acceptable when an intervening occational catalog update fails with a "VersionLockError". -- Dieter