On 10/31/07, Mario Ivankovits <[EMAIL PROTECTED]> wrote: > Hi! > >> Is it possible to describe "full attribute optimistic locking" in a couple > >> of sentences, or should I look at the cayenne docs? (A quick google didn't > >> show anything obviously related..) > >> > > > > Sure. Instead of creating and locking on a special version field, > > lock on all fields (or all that are important). Assuming table > > foo[w,x,y,z], use "update foo set x=1, y=1 where w=old_w, x=old_x, > > y=old_y, z=old_z" > > > Beware, (especially with the "or all that are important" thing) this > might allow to become your entity out of sync. Means, your entity is a > mixture of > different updates which you are not aware of then. > Using all properties of the version column (which might be more > performant) is the only option to prevent this.
Well, we're getting a bit off topic, but there's nothing to beware of here. If you lock on all columns which can change, then it will always work. If a column cannot change, then there's no need to lock on it. If in doubt, lock on them all -- it's the safest thing to do if there's no performance issues. F.A.O.L. has its downsides (requires caching of old attributes), but it has its upsides too -- works with any database and any database table without modification of schema, assuming all columns support equality operations.
