001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019package org.apache.hadoop.mapreduce.lib.db;
020
021import java.sql.ResultSet;
022import java.sql.SQLException;
023import java.util.ArrayList;
024import java.util.List;
025
026import org.apache.hadoop.classification.InterfaceAudience;
027import org.apache.hadoop.classification.InterfaceStability;
028import org.apache.hadoop.conf.Configuration;
029import org.apache.hadoop.mapreduce.InputSplit;
030import org.apache.hadoop.mapreduce.MRJobConfig;
031
032/**
033 * Implement DBSplitter over integer values.
034 */
035@InterfaceAudience.Public
036@InterfaceStability.Evolving
037public class IntegerSplitter implements DBSplitter {
038  public List<InputSplit> split(Configuration conf, ResultSet results, String colName)
039      throws SQLException {
040
041    long minVal = results.getLong(1);
042    long maxVal = results.getLong(2);
043
044    String lowClausePrefix = colName + " >= ";
045    String highClausePrefix = colName + " < ";
046
047    int numSplits = conf.getInt(MRJobConfig.NUM_MAPS, 1);
048    if (numSplits < 1) {
049      numSplits = 1;
050    }
051
052    if (results.getString(1) == null && results.getString(2) == null) {
053      // Range is null to null. Return a null split accordingly.
054      List<InputSplit> splits = new ArrayList<InputSplit>();
055      splits.add(new DataDrivenDBInputFormat.DataDrivenDBInputSplit(
056          colName + " IS NULL", colName + " IS NULL"));
057      return splits;
058    }
059
060    // Get all the split points together.
061    List<Long> splitPoints = split(numSplits, minVal, maxVal);
062    List<InputSplit> splits = new ArrayList<InputSplit>();
063
064    // Turn the split points into a set of intervals.
065    long start = splitPoints.get(0);
066    for (int i = 1; i < splitPoints.size(); i++) {
067      long end = splitPoints.get(i);
068
069      if (i == splitPoints.size() - 1) {
070        // This is the last one; use a closed interval.
071        splits.add(new DataDrivenDBInputFormat.DataDrivenDBInputSplit(
072            lowClausePrefix + Long.toString(start),
073            colName + " <= " + Long.toString(end)));
074      } else {
075        // Normal open-interval case.
076        splits.add(new DataDrivenDBInputFormat.DataDrivenDBInputSplit(
077            lowClausePrefix + Long.toString(start),
078            highClausePrefix + Long.toString(end)));
079      }
080
081      start = end;
082    }
083
084    if (results.getString(1) == null || results.getString(2) == null) {
085      // At least one extrema is null; add a null split.
086      splits.add(new DataDrivenDBInputFormat.DataDrivenDBInputSplit(
087          colName + " IS NULL", colName + " IS NULL"));
088    }
089
090    return splits;
091  }
092
093  /**
094   * Returns a list of longs one element longer than the list of input splits.
095   * This represents the boundaries between input splits.
096   * All splits are open on the top end, except the last one.
097   *
098   * So the list [0, 5, 8, 12, 18] would represent splits capturing the intervals:
099   *
100   * [0, 5)
101   * [5, 8)
102   * [8, 12)
103   * [12, 18] note the closed interval for the last split.
104   */
105  List<Long> split(long numSplits, long minVal, long maxVal)
106      throws SQLException {
107
108    List<Long> splits = new ArrayList<Long>();
109
110    // Use numSplits as a hint. May need an extra task if the size doesn't
111    // divide cleanly.
112
113    long splitSize = (maxVal - minVal) / numSplits;
114    if (splitSize < 1) {
115      splitSize = 1;
116    }
117
118    long curVal = minVal;
119
120    while (curVal <= maxVal) {
121      splits.add(curVal);
122      curVal += splitSize;
123    }
124
125    if (splits.get(splits.size() - 1) != maxVal || splits.size() == 1) {
126      // We didn't end on the maxVal. Add that to the end of the list.
127      splits.add(maxVal);
128    }
129
130    return splits;
131  }
132}