| /* |
| * 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.iotdb.db.storageengine.dataregion.read.reader.common; |
| |
| import org.apache.iotdb.db.utils.TimeValuePairUtils; |
| |
| import org.apache.tsfile.enums.TSDataType; |
| import org.apache.tsfile.read.TimeValuePair; |
| |
| import java.io.IOException; |
| |
| /** |
| * CachedPriorityMergeReader use a cache to reduce unnecessary heap updates and increase locality. |
| */ |
| public class CachedPriorityMergeReader extends PriorityMergeReader { |
| |
| private static final int CACHE_SIZE = 100; |
| |
| private TimeValuePair[] timeValuePairCache = new TimeValuePair[CACHE_SIZE]; |
| private int cacheLimit = 0; |
| private int cacheIdx = 0; |
| |
| private Long lastTimestamp = null; |
| |
| public CachedPriorityMergeReader(TSDataType dataType) { |
| for (int i = 0; i < CACHE_SIZE; i++) { |
| timeValuePairCache[i] = TimeValuePairUtils.getEmptyTimeValuePair(dataType); |
| } |
| } |
| |
| @Override |
| public boolean hasNextTimeValuePair() { |
| return cacheIdx < cacheLimit || !heap.isEmpty(); |
| } |
| |
| private void fetch() throws IOException { |
| cacheLimit = 0; |
| cacheIdx = 0; |
| while (!heap.isEmpty() && cacheLimit < CACHE_SIZE) { |
| Element top = heap.peek(); |
| if (lastTimestamp == null || top.currTime() != lastTimestamp) { |
| TimeValuePairUtils.setTimeValuePair( |
| top.getTimeValuePair(), timeValuePairCache[cacheLimit++]); |
| lastTimestamp = top.currTime(); |
| } |
| // remove duplicates |
| while (heap.peek() != null && heap.peek().currTime() == lastTimestamp) { |
| top = heap.poll(); |
| if (top.hasNext()) { |
| top.next(); |
| heap.add(top); |
| } else { |
| top.close(); |
| } |
| } |
| } |
| } |
| |
| @Override |
| public TimeValuePair nextTimeValuePair() throws IOException { |
| TimeValuePair ret; |
| if (cacheIdx < cacheLimit) { |
| ret = timeValuePairCache[cacheIdx++]; |
| } else { |
| fetch(); |
| ret = timeValuePairCache[cacheIdx++]; |
| } |
| return ret; |
| } |
| |
| @Override |
| public TimeValuePair currentTimeValuePair() throws IOException { |
| if (0 <= cacheIdx && cacheIdx < cacheLimit) { |
| return timeValuePairCache[cacheIdx]; |
| } else { |
| fetch(); |
| return timeValuePairCache[cacheIdx]; |
| } |
| } |
| } |