/*
* 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 org.apache.jena.sparql.engine.optimizer.reorder ;
import org.apache.jena.sparql.core.BasicPattern ;
import org.apache.jena.sparql.engine.optimizer.StatsMatcher ;
public class ReorderLib
{
private static class ReorderProcIdentity implements ReorderProc
{
@Override
public BasicPattern reorder(BasicPattern pattern) {
return pattern ;
}
@Override
public String toString() {
return "identity reorder" ;
}
}
private static ReorderProc _identityProc = new ReorderProcIdentity() ;
private static class ReorderTransformationIdentity implements ReorderTransformation
{
@Override
public BasicPattern reorder(BasicPattern pattern) {
return pattern ;
}
@Override
public ReorderProc reorderIndexes(BasicPattern pattern) {
return _identityProc ;
}
}
private static ReorderTransformation _identity = new ReorderTransformationIdentity() ;
/**
* Return a ReorderProc that does no reordering (leaving the query writer
* in-control)
*/
public static ReorderProc identityProc() {
return _identityProc ;
}
/**
* Return a ReorderTransformation that maps directly to the original
* (leaving the query writer in-control)
*/
public static ReorderTransformation identity() {
return _identity ;
}
/**
* Return a ReorderTransformation that performance some basic reordering
* based on most grounded triples first, but otherwise leaves things
* in query-written order.
*/
public static ReorderTransformation fixed() {
return new ReorderFixed() ;
}
/**
* Return a ReorderTransformation that uses statistics.
* <a href="https://jena.apache.org/documentation/tdb/optimizer.html">As used in TDB</a>.
*/
public static ReorderTransformation weighted(String filename) {
StatsMatcher stats = new StatsMatcher(filename) ;
return new ReorderWeighted(stats) ;
}
}