[rules-users] Can't obtain object from a FactHandle

[Davide Sottara]

When **from** is used, there is no guarantee that the objects
are part of the working memory - actually it is expected that they aren't,
otherwise a memberOf constraint would have probably been used.
Tentatively looking up a possibly-but-unlikely-existing fact handle for
each object would
have impacted performance negatively, so it was decided that **from**
would **always** create handles on the fly.
Of course, I agree that the integrity of the WM (and thus of the
universe) is broken,
albeit in a minor way :). We couldn't yet find a use case where this
inconsistency
would cause major issues.
I'd move the discussion to the drools-dev list anyway, if a major
problem - or
an efficient solution - could be proposed.
Best
Davide


On 03/02/2013 10:45 AM, Wolfgang Laun wrote:
> Given a
>    org.drools.event.rule.BeforeActivationFiredEvent,
> method getActivation() returns a
>    org.drools.runtime.rule.Activation
> and its method getFactHandles() is documented to return a List<FactHandle>.
>
> It should be possible to retrieve the fact object using
> session.getObject( factHandle ), and this succeeds in many instances,
> but not reliably (5.5.0-Final).
>
> Given facts of types One and Two a rule like
>    One( $list: listOFTwos )
>    Two(...) from $list
> I find that Two facts, when matched via from, are not reported with
> the proper fact handle, i.e., the one returned from the insert.
>
> What's the point in reporting fact handles that can't be used to
> retrieve a fact object?
>
> If I want to obtain all facts that participate in an activation, is
> method Activation.getObjects() more (and fully) reliable?
>
> -W
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