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https://issues.apache.org/jira/browse/JENA-120?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13109624#comment-13109624
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Andy Seaborne edited comment on JENA-120 at 9/21/11 4:22 PM:
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BindingKey don't mutate if everything is working because the Binding they
depend on should not change.
Bindings are create-once objects, the whole parent hierarchy helps that.
Changing a binding, not extending is via the partent mechanism, must only be
done in one step of the execution (e.g. a BGP evaluation or an assignment).
Once let out, it should be unchanging.
We can fix up the codebase to force this by removing .add and .addAll in
interface Binding.
A common pattern is
Binding b = new BindingMap(input) ;
and we just need to have:
BindingMap b = new BindingMap(input) ;
and/or BindingFactory.create() -> BindingMutable that does have .add/.addAll.
was (Author: andy.seaborne):
BindingKey don't mutate if everything is working because the Binding they
depend on should not change.
Bindings are create-once objects, the whole parent hierarchy helps that.
Changing a binding, not extending is via the partent mechanism, must only be
done in one step of the execution (e.g. a BGP evaluation or an assignment).
Once let out, it should be unchanging.
We can fix up the codebase to force this by removing .add and .addAll in
interface Binding.
A common pattern is
Binding b = new BindingMap(input) ;
and we just need to have:
BindingMap b = new BindingMap(input) ;
> Query objects with aggregators cannot be reused
> -----------------------------------------------
>
> Key: JENA-120
> URL: https://issues.apache.org/jira/browse/JENA-120
> 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]
> http://mail-archives.apache.org/mod_mbox/incubator-jena-users/201109.mbox/%3cb60aca3a-db31-4fec-a72e-d81a5c2ab...@knublauch.com%3E
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