[elephant-devel] Unique key with Elephant

[Ian Eslick]

I can't say I've thought deeply about this, but instance creation is wrapped in a transaction - so long as the side effects you are concerned about, including reads the store, they should be atomic due to BDB locking.

On Mar 18, 2010, at 6:37 AM, Alex Mizrahi wrote:

> IE> Should be easy to add an index lookup to shared-initialize and a check
> IE> in indexed slot access as to whether you are changing the unique value.
> 
> Hmm, there is a problem with this and concurrency -- one thread does a 
> check, it passes and it inserts a value, and another thread does the same 
> thing.
> Now there are two entries with same key, despite both checks passed.
> 
> Or will locks in BDB prevent this?
> 
> In PostgreSQL they do not, unless there is unique index in database. 
> 
> 
> 
> _______________________________________________
> elephant-devel site list
> elephant-devel at common-lisp.net
> http://common-lisp.net/mailman/listinfo/elephant-devel