Class ProjectionRemovalOptimizer

java.lang.Object

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

All Implemented Interfaces:

QueryOptimizer

public class ProjectionRemovalOptimizer
extends Object
implements QueryOptimizer

If a projection node in the algebra does not contribute or change the results it can be removed from the tree.

For example SELECT ?s ?p ?o WHERE {?s ?p ?o } Does not need a projection as the inner statement pattern returns the same result.

While * SELECT ?s ?p WHERE {?s ?p ?o } Does as the statement pattern has one more variable in use than the projection.

Note: this optimiser should run after optimisations ran that depend on Projections. e.g.

Author:

Jerven Bolleman

See Also:

• UnionScopeChangeOptimizer

Constructor Summary

Constructors

Constructor	Description
ProjectionRemovalOptimizer()

Method Summary

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

Methods inherited from class Object

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

Constructor Details

ProjectionRemovalOptimizer

public ProjectionRemovalOptimizer()

Method Details

optimize

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

Specified by:

optimize in interface QueryOptimizer