April 2003
Beginner to intermediate
380 pages
12h 25m
English
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Persistent-Nontransactional State
The use of instances outside a transaction introduces another
instance lifecycle state:
persistent-nontransactional . From the application program perspective, this state is
indistinguishable from the hollow state. That is, the results of
executing the interrogatives in JDOHelper (isNew(
), isDirty( ), etc.) are
the same for instances in both states. Your application generally should
not be aware of the difference between instances in the hollow and
persistent-nontransactional states.
From a performance perspective, your application might run faster, because accessing field values of instances in the persistent-nontransactional state might be done without a datastore access. Your application can retrieve field values cached in the instance and navigate the object graph to other instances, relying only on the cached values. The only time the datastore must be accessed is when a field that has not yet been loaded from the datastore is read.
With datastore transactions, existing persistent instances begin
their lifecycle in the cache as persistent-clean or persistent-dirty.
With the first access to persistent instances outside a transaction,
they begin their lifecycle in the cache in the
persistent-nontransactional state. This can be the result of an Extent iteration, a query execution, or
navigation from another persistent-nontransactional instance.
With NontransactionalRead
set to true, outside a
transaction:
Your application can read field values, ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.