| /** |
| * 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.hadoop.mapreduce.lib.aggregate; |
| |
| import java.util.ArrayList; |
| import java.util.Iterator; |
| import java.util.Set; |
| import java.util.TreeMap; |
| |
| /** |
| * This class implements a value aggregator that dedupes a sequence of objects. |
| * |
| */ |
| public class UniqValueCount implements ValueAggregator<Object> { |
| public static final String MAX_NUM_UNIQUE_VALUES = |
| "mapreduce.aggregate.max.num.unique.values"; |
| |
| private TreeMap<Object, Object> uniqItems = null; |
| |
| private long numItems = 0; |
| |
| private long maxNumItems = Long.MAX_VALUE; |
| |
| /** |
| * the default constructor |
| * |
| */ |
| public UniqValueCount() { |
| this(Long.MAX_VALUE); |
| } |
| |
| /** |
| * constructor |
| * @param maxNum the limit in the number of unique values to keep. |
| * |
| */ |
| public UniqValueCount(long maxNum) { |
| uniqItems = new TreeMap<Object, Object>(); |
| this.numItems = 0; |
| maxNumItems = Long.MAX_VALUE; |
| if (maxNum > 0 ) { |
| this.maxNumItems = maxNum; |
| } |
| } |
| |
| /** |
| * Set the limit on the number of unique values |
| * @param n the desired limit on the number of unique values |
| * @return the new limit on the number of unique values |
| */ |
| public long setMaxItems(long n) { |
| if (n >= numItems) { |
| this.maxNumItems = n; |
| } else if (this.maxNumItems >= this.numItems) { |
| this.maxNumItems = this.numItems; |
| } |
| return this.maxNumItems; |
| } |
| |
| /** |
| * add a value to the aggregator |
| * |
| * @param val |
| * an object. |
| * |
| */ |
| public void addNextValue(Object val) { |
| if (this.numItems <= this.maxNumItems) { |
| uniqItems.put(val.toString(), "1"); |
| this.numItems = this.uniqItems.size(); |
| } |
| } |
| |
| /** |
| * @return return the number of unique objects aggregated |
| */ |
| public String getReport() { |
| return "" + uniqItems.size(); |
| } |
| |
| /** |
| * |
| * @return the set of the unique objects |
| */ |
| public Set<Object> getUniqueItems() { |
| return uniqItems.keySet(); |
| } |
| |
| /** |
| * reset the aggregator |
| */ |
| public void reset() { |
| uniqItems = new TreeMap<Object, Object>(); |
| } |
| |
| /** |
| * @return return an array of the unique objects. The return value is |
| * expected to be used by the a combiner. |
| */ |
| public ArrayList<Object> getCombinerOutput() { |
| Object key = null; |
| Iterator<Object> iter = uniqItems.keySet().iterator(); |
| ArrayList<Object> retv = new ArrayList<Object>(); |
| |
| while (iter.hasNext()) { |
| key = iter.next(); |
| retv.add(key); |
| } |
| return retv; |
| } |
| } |