/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.hp.hpl.jena.sparql.algebra.optimize;
import com.hp.hpl.jena.sparql.algebra.Op;
import com.hp.hpl.jena.sparql.algebra.TransformCopy;
import com.hp.hpl.jena.sparql.algebra.op.OpBGP;
import com.hp.hpl.jena.sparql.algebra.op.OpQuadPattern;
import com.hp.hpl.jena.sparql.core.BasicPattern;
import com.hp.hpl.jena.sparql.engine.optimizer.reorder.ReorderLib;
import com.hp.hpl.jena.sparql.engine.optimizer.reorder.ReorderTransformation;
/**
* A Transformer that applies a reordering to all BGPs and Quad Patterns present in the algebra
* <p>
* This transformer may be slightly naive in that it only leverages the
* {@link ReorderTransformation#reorder(BasicPattern)} method and does not use
* the {@link ReorderTransformation#reorderIndexes(BasicPattern)} method at all
* so may not achieve the best reordering
* </p>
*/
public class TransformReorder extends TransformCopy {
private ReorderTransformation reorder;
/**
* Creates a Transformer that uses the fixed reordering provided by {@link ReorderLib#fixed()}
*/
public TransformReorder() {
this(ReorderLib.fixed());
}
/**
* Creates a Transformer that uses the given reordering
*/
public TransformReorder(ReorderTransformation reorder) {
if (reorder == null) throw new IllegalArgumentException("reorder cannot be null");
this.reorder = reorder;
}
/**
* Transforms BGPs with the reordering
*/
@Override
public Op transform(OpBGP opBGP) {
BasicPattern pattern = opBGP.getPattern();
BasicPattern pattern2 = this.reorder.reorder(pattern);
return new OpBGP(pattern2);
}
/**
* Transforms Quad Patterns with the reordering
*/
@Override
public Op transform(OpQuadPattern opQuadPattern) {
BasicPattern pattern = opQuadPattern.getBasicPattern();
BasicPattern pattern2 = this.reorder.reorder(pattern);
return new OpQuadPattern(opQuadPattern.getGraphNode(), pattern2);
}
}