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https://issues.apache.org/jira/browse/JENA-1148?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15169051#comment-15169051
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Eetu Mäkelä commented on JENA-1148:
-----------------------------------
If the data included {{<urn:b1> <urn:b2> <urn:x1>}}, should I not get
{{?s=<urn:b1>,?p=<urn:b2>,?o=<urn:x1>,?b=true}} out instead of just
{{?s=<urn:b1>,?p=<urn:b2>,?o=<urn:x1>}}?
In any case, the BIND is just a placeholder, it could be anything. Here's a
different practical example:
{code}
SELECT * {
?s a edm:ProvidedCHO .
?s ?p ?o .
OPTIONAL {
FILTER(?p=dct:spatial)
?o wgs84:lat ?lat .
?o wgs84:long ?long .
}
}
{code}
The idea being that in a single query, you get all properties for all cultural
heritage objects, but also if that property happens to be a relation between
the object and a place, then you also grab that place's coordinates. However,
currently, the above will never return any coordinates, because the optimizer
thinks {{?p}} can never be bound inside the block.
(the situation where I _actually_ encountered this included a SERVICE call
which needed to run only on certain predicates to get further info from a
separate service on the objects of those predicates)
> 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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