Hi, I have the query below which includes filter blocks.
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> PREFIX void: <http://rdfs.org/ns/void#> SELECT (COUNT(*) AS ?count) WHERE { ?referrerDataset rdf:type void:Dataset. FILTER (?referrerDataset IN(< http://datasets/geonames#indv_0.32581606535856833>, <http://datasets/linkedMdb#indv_0.7447588411027833> ) ) . ?linkset void:subjectsTarget ?referrerDataset. ?linkset void:linkPredicate <http://www.w3.org/2002/07/owl#sameAs>. ?linkset void:objectsTarget ?referencedDataset. ?referencedDataset1 rdf:type void:Dataset. FILTER NOT EXISTS {?referencedDataset void:sparqlEndpoint ?endpoint.} ?referencedDataset void:uriSpace ?uriSpace. } I placed the filter blocks in specific positions to ensure performance in the query. When executing the query, ARQ changes the positions of the filter blocks, and puts them at the end as seen below. PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> PREFIX void: <http://rdfs.org/ns/void#> SELECT (COUNT(*) AS ?count) WHERE { ?referrerDataset rdf:type void:Dataset. ?linkset void:subjectsTarget ?referrerDataset. ?linkset void:linkPredicate <http://www.w3.org/2002/07/owl#sameAs>. ?linkset void:objectsTarget ?referencedDataset. ?referencedDataset1 rdf:type void:Dataset. ?referencedDataset void:uriSpace ?uriSpace. FILTER (?referrerDataset IN(< http://datasets/geonames#indv_0.32581606535856833>, <http://datasets/linkedMdb#indv_0.7447588411027833> ) ) . FILTER NOT EXISTS {?referencedDataset void:sparqlEndpoint ?endpoint.} } I created the query above with the code below. But, the same thing occurs while I am using the QueryExecution.execSelect(). Query originalQuery = QueryFactory.create(queryStr); Op op = QueryExecutionFactory.createPlan(originalQuery, DatasetGraphFactory.createMem(), null).getOp(); Query changedQuery = OpAsQuery.asQuery(op); System.out.println(changedQuery); I have read in some threads in mailing list that ARQ optimizes the query and places the filter blocks to the best position in the query. I use ARQ 2.9.4, and my data is in a Jena in-memory model. Does anybody have an idea why ARQ moves the filter blocks to the end of the query? I don't think this is the best position for the filter blocks. Thank you. Best regards, Tayfun Gokmen Halac
