org.apache.cassandra.hadoop2.cql3.CqlPagingInputFormat.java Source code

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Here is the source code for org.apache.cassandra.hadoop2.cql3.CqlPagingInputFormat.java

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/*
 * 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.cassandra.hadoop2.cql3;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.Map;

import org.apache.cassandra.hadoop2.AbstractColumnFamilyInputFormat;
import org.apache.hadoop.mapred.InputSplit;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.RecordReader;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.TaskAttemptID;
import org.apache.hadoop.mapreduce.task.TaskAttemptContextImpl;

/**
 * Hadoop InputFormat allowing map/reduce against Cassandra rows within one
 * ColumnFamily.
 *
 * At minimum, you need to set the KS and CF in your Hadoop job Configuration.
 * The ConfigHelper class is provided to make this simple:
 * ConfigHelper.setInputColumnFamily
 *
 * You can also configure the number of rows per InputSplit with
 * ConfigHelper.setInputSplitSize. The default split size is 64k rows. the
 * number of CQL rows per page
 *
 * the number of CQL rows per page CQLConfigHelper.setInputCQLPageRowSize. The
 * default page row size is 1000. You should set it to "as big as possible, but
 * no bigger." It set the LIMIT for the CQL query, so you need set it big enough
 * to minimize the network overhead, and also not too big to avoid out of memory
 * issue.
 *
 * the column names of the select CQL query. The default is all columns
 * CQLConfigHelper.setInputColumns
 *
 * the user defined the where clause CQLConfigHelper.setInputWhereClauses. The
 * default is no user defined where clause
 */
public class CqlPagingInputFormat
        extends AbstractColumnFamilyInputFormat<Map<String, ByteBuffer>, Map<String, ByteBuffer>> {

    public RecordReader<Map<String, ByteBuffer>, Map<String, ByteBuffer>> getRecordReader(InputSplit split,
            JobConf jobConf, final Reporter reporter) throws IOException {
        TaskAttemptContext tac = new TaskAttemptContextImpl(jobConf,
                TaskAttemptID.forName(jobConf.get(MAPRED_TASK_ID))) {
            @Override
            public void progress() {
                reporter.progress();
            }
        };

        CqlPagingRecordReader recordReader = new CqlPagingRecordReader();
        recordReader.initialize((org.apache.hadoop.mapreduce.InputSplit) split, tac);
        return recordReader;
    }

    @Override
    public org.apache.hadoop.mapreduce.RecordReader<Map<String, ByteBuffer>, Map<String, ByteBuffer>> createRecordReader(
            org.apache.hadoop.mapreduce.InputSplit arg0, TaskAttemptContext arg1)
            throws IOException, InterruptedException {
        return new CqlPagingRecordReader();
    }

}