org.apache.hadoop.mapreduce.lib.db.IntegerSplitter.java Source code

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Here is the source code for org.apache.hadoop.mapreduce.lib.db.IntegerSplitter.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.hadoop.mapreduce.lib.db;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.MRJobConfig;

/**
 * Implement DBSplitter over integer values.
 */
@InterfaceAudience.Public
@InterfaceStability.Evolving
public class IntegerSplitter implements DBSplitter {
    public List<InputSplit> split(Configuration conf, ResultSet results, String colName) throws SQLException {

        long minVal = results.getLong(1);
        long maxVal = results.getLong(2);

        String lowClausePrefix = colName + " >= ";
        String highClausePrefix = colName + " < ";

        int numSplits = conf.getInt(MRJobConfig.NUM_MAPS, 1);
        if (numSplits < 1) {
            numSplits = 1;
        }

        if (results.getString(1) == null && results.getString(2) == null) {
            // Range is null to null. Return a null split accordingly.
            List<InputSplit> splits = new ArrayList<InputSplit>();
            splits.add(
                    new DataDrivenDBInputFormat.DataDrivenDBInputSplit(colName + " IS NULL", colName + " IS NULL"));
            return splits;
        }

        // Get all the split points together.
        List<Long> splitPoints = split(numSplits, minVal, maxVal);
        List<InputSplit> splits = new ArrayList<InputSplit>();

        // Turn the split points into a set of intervals.
        long start = splitPoints.get(0);
        for (int i = 1; i < splitPoints.size(); i++) {
            long end = splitPoints.get(i);

            if (i == splitPoints.size() - 1) {
                // This is the last one; use a closed interval.
                splits.add(new DataDrivenDBInputFormat.DataDrivenDBInputSplit(
                        lowClausePrefix + Long.toString(start), colName + " <= " + Long.toString(end)));
            } else {
                // Normal open-interval case.
                splits.add(new DataDrivenDBInputFormat.DataDrivenDBInputSplit(
                        lowClausePrefix + Long.toString(start), highClausePrefix + Long.toString(end)));
            }

            start = end;
        }

        if (results.getString(1) == null || results.getString(2) == null) {
            // At least one extrema is null; add a null split.
            splits.add(
                    new DataDrivenDBInputFormat.DataDrivenDBInputSplit(colName + " IS NULL", colName + " IS NULL"));
        }

        return splits;
    }

    /**
     * Returns a list of longs one element longer than the list of input splits.
     * This represents the boundaries between input splits.
     * All splits are open on the top end, except the last one.
     *
     * So the list [0, 5, 8, 12, 18] would represent splits capturing the intervals:
     *
     * [0, 5)
     * [5, 8)
     * [8, 12)
     * [12, 18] note the closed interval for the last split.
     */
    List<Long> split(long numSplits, long minVal, long maxVal) throws SQLException {

        List<Long> splits = new ArrayList<Long>();

        // Use numSplits as a hint. May need an extra task if the size doesn't
        // divide cleanly.

        long splitSize = (maxVal - minVal) / numSplits;
        if (splitSize < 1) {
            splitSize = 1;
        }

        long curVal = minVal;

        while (curVal <= maxVal) {
            splits.add(curVal);
            curVal += splitSize;
        }

        if (splits.get(splits.size() - 1) != maxVal || splits.size() == 1) {
            // We didn't end on the maxVal. Add that to the end of the list.
            splits.add(maxVal);
        }

        return splits;
    }
}