Re: Handling exceptions in saveChanges() (Was: "Cannot obtain globalId for an object which...")
Re: Handling exceptions in saveChanges() (Was: "Cannot obtain globalId for an object which...")
- Subject: Re: Handling exceptions in saveChanges() (Was: "Cannot obtain globalId for an object which...")
- From: Jonathan Rochkind <email@hidden>
- Date: Wed, 11 Jun 2003 11:32:17 -0500
At 04:46 PM 6/10/2003 -0700, Chuck Hill wrote:
This could be interesting. How can this be done in a multi-threaded or
multi-instance application? I think that the database is the only place
where unique constraints (e.g. a user ID) can be checked without risking
race conditions. Optimistic locking failures can be avoided with
pessimistic locking at the database - something to be avoided IMHO. They
can also be avoided by a "last write wins" strategy of forcing the update
or by not checking for failures at all. Neither of those seem like a
good, general purpose solution.
Not a good general purpose solution, true, but in my own apps, I decided
that a 'last write wins' strategy is actually just fine. And implementing
it is easy as pie---simply turn off the lock icon for all attributes but
for primary key attributes, and you'll never have to deal with optimistic
locking failures again. [Well, mostly. There are some cases where something
that could conceptually be considered an optimistic locking failure can
still occur---like adding a many-to-many relation that was just created by
some other instance, causing a 'duplicate pk insertion' error for the join
object. But you're 90% off the hook].
Understandably, this isn't an acceptable strategy for a great many apps.
But many developers don't even seem to consider it, they seem to assume
that they need optimistic locking. It's worth considering. If a 'last write
wins' strategy is acceptable for your app, you can save yourself a whole
lot of trouble.
--Jonathan
Cheers,
Chuck
--
Chuck Hill email@hidden
Global Village Consulting Inc. http://www.global-village.net
Progress is the mother of all problems.
- G. K. Chesterton
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