org.apache.hadoop.hive.ql.exec.persistence.HashMapWrapper Maven / Gradle / Ivy
/**
* 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.hive.ql.exec.persistence;
import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
/**
* Simple wrapper for persistent Hashmap implementing only the put/get/remove/clear interface. The
* main memory hash table acts as a cache and all put/get will operate on it first. If the size of
* the main memory hash table exceeds a certain threshold, new elements will go into the persistent
* hash table.
*/
public class HashMapWrapper extends AbstractMapJoinTableContainer implements Serializable {
private static final long serialVersionUID = 1L;
protected static final Log LOG = LogFactory.getLog(HashMapWrapper.class);
// default threshold for using main memory based HashMap
private static final String THESHOLD_NAME = "threshold";
private static final String LOAD_NAME = "load";
private static final int THRESHOLD = 1000000;
private static final float LOADFACTOR = 0.75f;
private HashMap mHash; // main memory HashMap
/**
* Constructor.
*
* @param threshold
* User specified threshold to store new values into persistent storage.
*/
public HashMapWrapper(int threshold, float loadFactor) {
super(createConstructorMetaData(threshold, loadFactor));
mHash = new HashMap(threshold, loadFactor);
}
public HashMapWrapper(Map metaData) {
super(metaData);
int threshold = Integer.parseInt(metaData.get(THESHOLD_NAME));
float loadFactor = Float.parseFloat(metaData.get(LOAD_NAME));
mHash = new HashMap(threshold, loadFactor);
}
public HashMapWrapper(int threshold) {
this(threshold, LOADFACTOR);
}
public HashMapWrapper() {
this(THRESHOLD, LOADFACTOR);
}
@Override
public MapJoinRowContainer get(MapJoinKey key) {
return mHash.get(key);
}
@Override
public void put(MapJoinKey key, MapJoinRowContainer value) {
mHash.put(key, value);
}
@Override
public int size() {
return mHash.size();
}
@Override
public Set> entrySet() {
return mHash.entrySet();
}
@Override
public void clear() {
mHash.clear();
}
private static Map createConstructorMetaData(int threshold, float loadFactor) {
Map metaData = new HashMap();
metaData.put(THESHOLD_NAME, String.valueOf(threshold));
metaData.put(LOAD_NAME, String.valueOf(loadFactor));
return metaData;
}
@Override
public MapJoinKey getAnyKey() {
return mHash.isEmpty() ? null : mHash.keySet().iterator().next();
}
}