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https://issues.apache.org/jira/browse/JENA-2020?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17258418#comment-17258418
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Martin Pekár commented on JENA-2020:
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But in the query plan, {{OpExistence}} is the second last operator just before
{{OpBGP}}. If I do nothing but immediately call {{exec()}} with the sub
operator of {{OpExistence}} (which is a {{OpBGP}}), then I should get the same
result as if {{OpExistence}} wasn't in the query plan. I have debugged both the
concretise code and the {{OpExistence}} itself, and everything seems to be as
it should be. The shorthand if-statement is also true in all the cases it
should be, so the last call to {{exec()}} should return a result just as if the
{{OpExistence}} operator wasn't present.
It also seems weird the iterator hasn't been used and returns that warning. The
{{StageGenerator}} should make use of it.
> 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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