src/java/org/apache/hcatalog/rcfile/RCFileMapReduceRecordReader.java

/**
 * 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.hcatalog.rcfile;

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hive.ql.io.RCFile;
import org.apache.hadoop.hive.ql.io.RCFile.Reader;
import org.apache.hadoop.hive.serde2.columnar.BytesRefArrayWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.lib.input.FileSplit;

public class RCFileMapReduceRecordReader<K extends LongWritable, V extends BytesRefArrayWritable>
    extends RecordReader<LongWritable, BytesRefArrayWritable> {

    private Reader in;
    private long start;
    private long end;
    private boolean more = true;

    // key and value objects are created once in initialize() and then reused
    // for every getCurrentKey() and getCurrentValue() call. This is important
    // since RCFile makes an assumption of this fact.

    private LongWritable key;
    private BytesRefArrayWritable value;

    @Override
    public void close() throws IOException {
        in.close();
    }

    @Override
    public LongWritable getCurrentKey() throws IOException, InterruptedException {
        return key;
    }

    @Override
    public BytesRefArrayWritable getCurrentValue() throws IOException, InterruptedException {
        return value;
    }

    @Override
    public float getProgress() throws IOException, InterruptedException {
        if (end == start) {
            return 0.0f;
        } else {
            return Math.min(1.0f, (in.getPosition() - start) / (float) (end - start));
        }
    }

    @Override
    public boolean nextKeyValue() throws IOException, InterruptedException {

        more = next(key);
        if (more) {
            in.getCurrentRow(value);
        }

        return more;
    }

    private boolean next(LongWritable key) throws IOException {
        if (!more) {
            return false;
        }

        more = in.next(key);
        if (!more) {
            return false;
        }

        if (in.lastSeenSyncPos() >= end) {
            more = false;
            return more;
        }
        return more;
    }

    @Override
    public void initialize(InputSplit split, TaskAttemptContext context) throws IOException,
        InterruptedException {

        FileSplit fSplit = (FileSplit) split;
        Path path = fSplit.getPath();
        Configuration conf = context.getConfiguration();
        this.in = new RCFile.Reader(path.getFileSystem(conf), path, conf);
        this.end = fSplit.getStart() + fSplit.getLength();

        if (fSplit.getStart() > in.getPosition()) {
            in.sync(fSplit.getStart());
        }

        this.start = in.getPosition();
        more = start < end;

        key = new LongWritable();
        value = new BytesRefArrayWritable();
    }
}