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https://issues.apache.org/jira/browse/JENA-1148?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15169011#comment-15169011
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Rob Vesse commented on JENA-1148:
---------------------------------

Are you expecting the {{FILTER}} to apply over the left join rather than just 
within the {{OPTIONAL}} block? In which case can you try moving the {{FILTER}} 
after the {{BIND}} because where {{BIND}} is involved placement in the query is 
significant

> TransformFilterEquality incorrectly eliminates some optionals
> -------------------------------------------------------------
>
>                 Key: JENA-1148
>                 URL: https://issues.apache.org/jira/browse/JENA-1148
>             Project: Apache Jena
>          Issue Type: Bug
>          Components: ARQ
>            Reporter: Eetu Mäkelä
>              Labels: Optimization, sparql
>
> For a query of the form:
> {code}
> SELECT * {
>   ?s ?p ?o
>   OPTIONAL {
>     FILTER(?o=<urn:x1>)
>     BIND(true AS ?b)
>   }
> }
> {code}
> ARQ optimization incorrectly eliminates the whole OPTIONAL when the variable 
> filtered on does not appear elsewhere inside the OPTIONAL block . This is 
> because of the special case check called on [line 120 of 
> TransformFilterEquality.java|https://git-wip-us.apache.org/repos/asf?p=jena.git;a=blob;f=jena-arq/src/main/java/org/apache/jena/sparql/algebra/optimize/TransformFilterEquality.java;h=38ba84019ba3b446afd8106128c517913a7ef73e;hb=6908fb7b7a500a70edb314b4830a18ed02a6b0f8#l120],
>  which sees that ?o is not used inside the block of the filter and thus (in 
> this case incorrectly) deduces that it could never be <urn:x1>.



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