org.apache.gora.mapreduce.GoraRecordReader.java Source code

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Here is the source code for org.apache.gora.mapreduce.GoraRecordReader.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.gora.mapreduce;

import java.io.IOException;

import org.apache.gora.persistency.Persistent;
import org.apache.gora.persistency.impl.PersistentBase;
import org.apache.gora.query.Query;
import org.apache.gora.query.Result;
import org.apache.gora.query.impl.ResultBase;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * An adapter for Result to Hadoop RecordReader.
 */
public class GoraRecordReader<K, T extends PersistentBase> extends RecordReader<K, T> {
    public static final Logger LOG = LoggerFactory.getLogger(GoraRecordReader.class);

    public static final String BUFFER_LIMIT_READ_NAME = "gora.buffer.read.limit";
    public static final int BUFFER_LIMIT_READ_VALUE = 10000;

    protected Query<K, T> query;
    protected Result<K, T> result;

    private GoraRecordCounter counter = new GoraRecordCounter();

    public GoraRecordReader(Query<K, T> query, TaskAttemptContext context) {
        this.query = query;

        Configuration configuration = context.getConfiguration();
        int recordsMax = configuration.getInt(BUFFER_LIMIT_READ_NAME, BUFFER_LIMIT_READ_VALUE);

        // Check if result set will at least contain 2 rows
        if (recordsMax <= 1) {
            LOG.info("Limit " + recordsMax + " changed to " + BUFFER_LIMIT_READ_VALUE);
            recordsMax = BUFFER_LIMIT_READ_VALUE;
        }

        counter.setRecordsMax(recordsMax);
        LOG.info("gora.buffer.read.limit = " + recordsMax);

        this.query.setLimit(recordsMax);
    }

    public void executeQuery() throws IOException, Exception {
        this.result = query.execute();
    }

    @Override
    public K getCurrentKey() throws IOException, InterruptedException {
        return result.getKey();
    }

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

    @Override
    public float getProgress() throws IOException, InterruptedException {
        try {
            return result.getProgress();
        } catch (Exception e) {
            return 0;
        }
    }

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

    @Override
    public boolean nextKeyValue() throws IOException, InterruptedException {
        try {
            if (counter.isModulo()) {
                boolean firstBatch = (this.result == null);
                if (!firstBatch) {
                    this.query.setStartKey(this.result.getKey());
                    if (this.query.getLimit() == counter.getRecordsMax()) {
                        this.query.setLimit(counter.getRecordsMax() + 1);
                    }
                }
                if (this.result != null) {
                    this.result.close();
                }

                executeQuery();

                if (!firstBatch) {
                    // skip first result
                    this.result.next();
                }
            }

            counter.increment();
            return this.result.next();
        } catch (Exception e) {
            LOG.error("Error reading Gora records");
            e.printStackTrace();
            return false;
        }
    }

    //@Override
    public void close() throws IOException {
        if (result != null) {
            result.close();
        }
    }

}