| /* |
| * 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.api.function.join; |
| |
| import static java.util.Objects.requireNonNull; |
| |
| import java.util.Iterator; |
| |
| import org.apache.rya.api.function.join.LazyJoiningIterator.Side; |
| import org.apache.rya.api.model.VisibilityBindingSet; |
| |
| import edu.umd.cs.findbugs.annotations.DefaultAnnotation; |
| import edu.umd.cs.findbugs.annotations.NonNull; |
| |
| /** |
| * Implements an {@link IterativeJoin} that uses the Natural Join algorithm |
| * defined by Relational Algebra. |
| * <p> |
| * This is how you combine {@code BindnigSet}s that may have common Binding |
| * names. When two Binding Sets are joined, any bindings that appear in both |
| * binding sets are only included once. |
| */ |
| @DefaultAnnotation(NonNull.class) |
| public class NaturalJoin implements IterativeJoin { |
| @Override |
| public Iterator<VisibilityBindingSet> newLeftResult(final VisibilityBindingSet newLeftResult, |
| final Iterator<VisibilityBindingSet> rightResults) { |
| requireNonNull(newLeftResult); |
| requireNonNull(rightResults); |
| |
| // Both sides are required, so if there are no right results, then do |
| // not emit anything. |
| return new LazyJoiningIterator(Side.LEFT, newLeftResult, rightResults); |
| } |
| |
| @Override |
| public Iterator<VisibilityBindingSet> newRightResult(final Iterator<VisibilityBindingSet> leftResults, |
| final VisibilityBindingSet newRightResult) { |
| requireNonNull(leftResults); |
| requireNonNull(newRightResult); |
| |
| // Both sides are required, so if there are no left reuslts, then do not |
| // emit anything. |
| return new LazyJoiningIterator(Side.RIGHT, newRightResult, leftResults); |
| } |
| } |