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https://issues.apache.org/jira/browse/JENA-2020?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17258524#comment-17258524
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Martin Pekár commented on JENA-2020:
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It seems like I need to copy the input iterator twice without consuming it.
It's probably an unanswerable question, but any ideas why just returning
\{{exec}} with the {{OpBGP}} in the {{subOp}} of {{OpExistence}} and {{input}}
returns an empty QueryIterator? Because, this is exactly what {{OpExistence}}
is supposed to do after doing some check.
> Purpose of EvaluatorSimple and OpExecutor
> -----------------------------------------
>
> Key: JENA-2020
> URL: https://issues.apache.org/jira/browse/JENA-2020
> Project: Apache Jena
> Issue Type: Question
> Components: ARQ
> Reporter: Martin Pekár
> Priority: Major
> Original Estimate: 1h
> Remaining Estimate: 1h
>
> I am in the midst of adding a new operator in the transformation of OpBGP. I
> am now trying to implement the execution of the operator in the query plan,
> but I am now slightly confused about the purpose of EvaluatorSimple used in
> EvaluatorDispatch and OpExecutor. At the moment, it seems like they are doing
> the same thing. The difference seems to be that OpExecutor stores the result
> of applying the operator in a QueryIterator, whereas EvaluatorSimple stores
> its result in a Table of bindings.
> Can someone give me an explanation of purposes of these two classes and how
> they should be used?
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