| /* |
| * 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.phoenix.iterate; |
| |
| import java.sql.SQLException; |
| import java.util.Comparator; |
| import java.util.List; |
| import java.util.PriorityQueue; |
| |
| import org.apache.hadoop.hbase.io.ImmutableBytesWritable; |
| import org.apache.phoenix.schema.tuple.Tuple; |
| |
| /** |
| * Base class for a ResultIterator that does a merge sort on the list of iterators provided. |
| * @since 1.2 |
| */ |
| public abstract class MergeSortResultIterator implements PeekingResultIterator { |
| protected final ResultIterators resultIterators; |
| protected final ImmutableBytesWritable tempPtr = new ImmutableBytesWritable(); |
| private PriorityQueue<MaterializedComparableResultIterator> minHeap; |
| private final IteratorComparator itrComparator = new IteratorComparator(); |
| |
| public MergeSortResultIterator(ResultIterators iterators) { |
| this.resultIterators = iterators; |
| } |
| |
| @Override |
| public void close() throws SQLException { |
| resultIterators.close(); |
| } |
| |
| abstract protected int compare(Tuple t1, Tuple t2); |
| |
| @Override |
| public Tuple peek() throws SQLException { |
| MaterializedComparableResultIterator iterator = minIterator(); |
| if (iterator == null) { return null; } |
| return iterator.peek(); |
| } |
| |
| @Override |
| public Tuple next() throws SQLException { |
| MaterializedComparableResultIterator iterator = minIterator(); |
| if (iterator == null) { return null; } |
| Tuple next = iterator.next(); |
| minHeap.poll(); |
| if (iterator.peek() != null) { |
| minHeap.add(iterator); |
| } else { |
| iterator.close(); |
| } |
| return next; |
| } |
| |
| private PriorityQueue<MaterializedComparableResultIterator> getMinHeap() throws SQLException { |
| if (minHeap == null) { |
| List<PeekingResultIterator> iterators = resultIterators.getIterators(); |
| minHeap = new PriorityQueue<MaterializedComparableResultIterator>(Math.max(1, iterators.size())); |
| for (PeekingResultIterator itr : iterators) { |
| if (itr.peek() == null) { |
| itr.close(); |
| continue; |
| } |
| minHeap.add(new MaterializedComparableResultIterator(itr, itrComparator)); |
| } |
| } |
| return minHeap; |
| } |
| |
| private class IteratorComparator implements Comparator<Tuple> { |
| @Override |
| public int compare(Tuple c1, Tuple c2) { |
| return MergeSortResultIterator.this.compare(c1, c2); |
| } |
| } |
| |
| private MaterializedComparableResultIterator minIterator() throws SQLException { |
| PriorityQueue<MaterializedComparableResultIterator> minHeap = getMinHeap(); |
| MaterializedComparableResultIterator minIterator = minHeap.peek(); |
| return minIterator; |
| } |
| |
| } |