com.ci.backports.avro.mapreduce.AvroRecordReader.java Source code

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Here is the source code for com.ci.backports.avro.mapreduce.AvroRecordReader.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 com.ci.backports.avro.mapreduce;

import java.io.IOException;

import org.apache.hadoop.io.NullWritable;
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;

import org.apache.avro.Schema;
import org.apache.avro.file.DataFileReader;
import org.apache.avro.file.SeekableInput;
import org.apache.avro.mapred.AvroKey;
import org.apache.avro.mapred.FsInput;
import org.apache.avro.specific.SpecificDatumReader;

/**
 * A {@link org.apache.hadoop.mapreduce.RecordReader} for Avro container files.
 */
public class AvroRecordReader<T> extends RecordReader<AvroKey<T>, NullWritable> {

    /** An Avro file reader that knows how to seek to record boundries. */
    private DataFileReader<T> reader;
    /** Start of the input split in bytes offset. */
    private long start;
    /** End of the input split in bytes offset. */
    private long end;
    /** Current record from the input split. */
    private AvroKey<T> currentRecord;

    @Override
    public void initialize(InputSplit split, TaskAttemptContext context) throws IOException, InterruptedException {
        FileSplit fileSplit = (FileSplit) split;
        // Create a DataFileReader that can read records out of the input split.
        SeekableInput fileInput = new FsInput(fileSplit.getPath(), context.getConfiguration());
        // We have to get the schema to read the records, which we assume was set in
        // the job's configuration.
        Schema schema = AvroJob.getInputSchema(context.getConfiguration());
        reader = new DataFileReader<T>(fileInput, new SpecificDatumReader<T>(schema));

        // Initialize the start and end offsets into the input file.
        // The reader syncs to the first record after the start of the input split.
        reader.sync(fileSplit.getStart());
        start = reader.previousSync();
        end = fileSplit.getStart() + fileSplit.getLength();

        currentRecord = new AvroKey<T>(null);
    }

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

    @Override
    public AvroKey<T> getCurrentKey() throws IOException, InterruptedException {
        return currentRecord;
    }

    @Override
    public NullWritable getCurrentValue() throws IOException, InterruptedException {
        return NullWritable.get();
    }

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

    @Override
    public boolean nextKeyValue() throws IOException, InterruptedException {
        if (reader.hasNext() && !reader.pastSync(end)) {
            currentRecord.datum(reader.next(currentRecord.datum()));
            return true;
        }
        return false;
    }
}