public class TransformFilterEquality extends TransformCopy
SELECT * WHERE { ?s ?p ?o . FILTER(?s = <http://subject>) }Would transform to the following:
SELECT * WHERE { <http://subject> ?p ?o . BIND(<http://subject> AS ?s) }
This optimizer is conservative in that it only makes the optimization where the equality constraint is against a non-literal as otherwise substituting the value changes the query semantics because it switches from value equality to the more restrictive term equality. The optimization is safe for non-literals because for those value and term equality are equivalent (in fact value equality is defined to be term equality).
There are also various nested algebra structures that can make the optimization unsafe and so it does not take place if any of those situations is detected.
COPY_ALWAYS, COPY_ONLY_ON_CHANGE
Constructor and Description |
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TransformFilterEquality() |
Modifier and Type | Method and Description |
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Op |
transform(OpFilter opFilter,
Op subOp) |
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Licenced under the Apache License, Version 2.0