Peter Eisentraut wrote:
> On Thursday 28 May 2009 04:49:19 Tom Lane wrote:
>> Yeah. The fundamental problem with all the "practical" approaches I've
>> heard of is that they only work for a subset of possible predicates
>> (possible WHERE clauses). The idea that you get true serializability
>> only if your queries are phrased just so is ... icky. So icky that
>> it doesn't sound like an improvement over what we have.
>
> Is it even possible to have a predicate locking implementation that can verify
> whether an arbitrary predicate implies another arbitrary predicate?
I don't think you need that for predicate locking. To determine if e.g
an INSERT and a SELECT conflict, you need to determine if the INSERTed
tuple matches the predicate in the SELECT. No need to deduce anything
between two predicates, but between a tuple and a predicate.
-- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com