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From "Stephen Allen (JIRA)" <>
Subject [jira] [Commented] (JENA-120) Query objects with aggregators cannot be reused
Date Thu, 22 Sep 2011 15:38:26 GMT


Stephen Allen commented on JENA-120:

That is probably the solution we want.

Also, looking at JENA-119, I think we might consider at some point how we would go about spilling
the state to disk.  The number of accumulators may be unbounded in size (although I'm not
sure how likely it is in practice that real queries would have enough groups to exhaust memory).

> Query objects with aggregators cannot be reused
> -----------------------------------------------
>                 Key: JENA-120
>                 URL:
>             Project: Jena
>          Issue Type: Bug
>          Components: ARQ
>            Reporter: Stephen Allen
>            Assignee: Andy Seaborne
>            Priority: Minor
>         Attachments: JENA-120-r1173178.patch, JENA-120-r1173729.patch, JENA-120-r1173738.patch
> Query objects that contain aggregators (Group By) cannot be reused by different threads
because the internal state is mutable.  Even reusing a query object in the same thread has
problems, because it creates a new Aggregator object each time you execute the query.  Users
may want to reuse Query objects to save having to reparse the query string.
> I believe the solution is to copy the aggregators when compiling the query.  I've attached
a patch that does that in the AlgebraGenerator.compileModifiers() method.
> See the thread at [1] for more discussion.
> [1]

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