| /* |
| * 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.rya.indexing.pcj.storage.accumulo; |
| |
| import static java.util.Objects.requireNonNull; |
| |
| import java.util.HashSet; |
| import java.util.List; |
| import java.util.Set; |
| |
| import edu.umd.cs.findbugs.annotations.DefaultAnnotation; |
| import edu.umd.cs.findbugs.annotations.NonNull; |
| |
| import org.openrdf.query.MalformedQueryException; |
| import org.openrdf.query.parser.sparql.SPARQLParser; |
| |
| import com.google.common.collect.Lists; |
| |
| /** |
| * Shifts the variables to the left so that each variable will appear at |
| * the head of the varOrder once. |
| */ |
| @DefaultAnnotation(NonNull.class) |
| public class ShiftVarOrderFactory implements PcjVarOrderFactory { |
| |
| @Override |
| public Set<VariableOrder> makeVarOrders(final String sparql) throws MalformedQueryException { |
| requireNonNull(sparql); |
| |
| final Set<String> bindingNames = new SPARQLParser().parseQuery(sparql, null) |
| .getTupleExpr() |
| .getBindingNames(); |
| |
| |
| return makeVarOrders( new VariableOrder(bindingNames) ); |
| } |
| |
| @Override |
| public Set<VariableOrder> makeVarOrders(final VariableOrder varOrder) { |
| final Set<VariableOrder> varOrders = new HashSet<>(); |
| |
| final List<String> cyclicBuff = Lists.newArrayList( varOrder.getVariableOrders() ); |
| final String[] varOrderBuff = new String[ cyclicBuff.size() ]; |
| |
| for(int shift = 0; shift < cyclicBuff.size(); shift++) { |
| // Build a variable order. |
| for(int i = 0; i < cyclicBuff.size(); i++) { |
| varOrderBuff[i] = cyclicBuff.get(i); |
| } |
| varOrders.add( new VariableOrder(varOrderBuff) ); |
| |
| // Shift the order the variables will appear in the cyclic buffer. |
| cyclicBuff.add( cyclicBuff.remove(0) ); |
| } |
| |
| return varOrders; |
| } |
| } |