package org.apache.cassandra.hadoop;
/*
*
* 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.
*
*/
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.apache.cassandra.db.Column;
import org.apache.cassandra.db.IColumn;
import org.apache.hadoop.mapreduce.Reducer;
/**
* The <code>ColumnFamilyOutputReducer</code> reduces a <key, values>
* pair, where the value is a generic iterable type, into a list of columns that
* need to be mutated for that key, where each column corresponds to an element
* in the value.
*
* <p>
* The default implementation treats the VALUEIN type to be a
* {@link ColumnWritable}, in which case this reducer acts as an identity
* function.
*
* @author Karthick Sankarachary
*
* @param <KEYIN>
*/
public class ColumnFamilyOutputReducer<KEYIN, VALUEIN> extends Reducer<KEYIN, VALUEIN, byte[], List<IColumn>>
{
public void reduce(KEYIN key, Iterable<VALUEIN> values, Context context) throws IOException, InterruptedException
{
byte[] cfKey = key.toString().getBytes();
List<IColumn> cfColumns = new ArrayList<IColumn>();
for (VALUEIN value : values)
{
ColumnWritable columnValue = map(value);
cfColumns.add(new Column(columnValue.getName(), columnValue.getValue()));
}
context.write(cfKey, cfColumns);
}
protected ColumnWritable map(VALUEIN value)
{
return (ColumnWritable) value;
}
}