Package org.eclipse.rdf4j.query.algebra.evaluation.optimizer

Class FilterOptimizer

java.lang.Object

org.eclipse.rdf4j.query.algebra.evaluation.optimizer.FilterOptimizer

All Implemented Interfaces:

QueryOptimizer

public class FilterOptimizer
extends Object
implements QueryOptimizer

Optimizes a query model by pushing Filters as far down in the model tree as possible.

To make the first optimization succeed more often it splits filters which contains And conditions.

SELECT * WHERE { \t?s ?p ?o . \t?s ?p ?o2 . \tFILTER(?o > '2'^^xsd:int && ?o2 < '4'^^xsd:int) } May be more efficient when decomposed into: SELECT * WHERE { \t?s ?p ?o . \tFILTER(?o > '2'^^xsd:int) \t?s ?p ?o2 . \tFILTER(?o2 < '4'^^xsd:int) }

Then it optimizes a query model by merging adjacent Filters. e.g. SELECT * WHERE { \t?s ?p ?o . \tFILTER(?o > 2) . \tFILTER(?o < 4) . } May be merged into: SELECT * WHERE { \t?s ?p ?o . \tFILTER(?o > 2 && ?o < 4) . }

This optimization allows for sharing evaluation costs in the future and removes an iterator. This is done as a second step to not break the first optimization. In the case that the splitting was done but did not help it is now undone.

Author:

Arjohn Kampman, Jerven Bolleman

Constructor Summary

Constructors

Constructor	Description
FilterOptimizer()

Method Summary

Modifier and Type	Method	Description
void	optimize(TupleExpr tupleExpr, Dataset dataset, BindingSet bindings)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

FilterOptimizer

public FilterOptimizer()

Method Detail

optimize

public void optimize(TupleExpr tupleExpr,
                     Dataset dataset,
                     BindingSet bindings)

Specified by:

optimize in interface QueryOptimizer