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.io.DataInput;
022import java.io.DataOutput;
023import java.io.IOException;
024import java.sql.Connection;
025import java.sql.DatabaseMetaData;
026import java.sql.PreparedStatement;
027import java.sql.ResultSet;
028import java.sql.SQLException;
029import java.sql.Statement;
030import java.util.ArrayList;
031import java.util.List;
032
033import org.apache.commons.logging.Log;
034import org.apache.commons.logging.LogFactory;
035import org.apache.hadoop.io.LongWritable;
036import org.apache.hadoop.io.Writable;
037import org.apache.hadoop.mapreduce.InputFormat;
038import org.apache.hadoop.mapreduce.InputSplit;
039import org.apache.hadoop.mapreduce.Job;
040import org.apache.hadoop.mapreduce.JobContext;
041import org.apache.hadoop.mapreduce.RecordReader;
042import org.apache.hadoop.mapreduce.TaskAttemptContext;
043import org.apache.hadoop.util.ReflectionUtils;
044import org.apache.hadoop.classification.InterfaceAudience;
045import org.apache.hadoop.classification.InterfaceStability;
046import org.apache.hadoop.conf.Configurable;
047import org.apache.hadoop.conf.Configuration;
048
049/**
050 * A RecordReader that reads records from a SQL table,
051 * using data-driven WHERE clause splits.
052 * Emits LongWritables containing the record number as
053 * key and DBWritables as value.
054 */
055@InterfaceAudience.Public
056@InterfaceStability.Evolving
057public class DataDrivenDBRecordReader<T extends DBWritable> extends DBRecordReader<T> {
058
059  private static final Log LOG = LogFactory.getLog(DataDrivenDBRecordReader.class);
060
061  private String dbProductName; // database manufacturer string.
062
063  /**
064   * @param split The InputSplit to read data for
065   * @throws SQLException 
066   */
067  public DataDrivenDBRecordReader(DBInputFormat.DBInputSplit split,
068      Class<T> inputClass, Configuration conf, Connection conn, DBConfiguration dbConfig,
069      String cond, String [] fields, String table, String dbProduct)
070      throws SQLException {
071    super(split, inputClass, conf, conn, dbConfig, cond, fields, table);
072    this.dbProductName = dbProduct;
073  }
074
075  /** Returns the query for selecting the records,
076   * subclasses can override this for custom behaviour.*/
077  @SuppressWarnings("unchecked")
078  protected String getSelectQuery() {
079    StringBuilder query = new StringBuilder();
080    DataDrivenDBInputFormat.DataDrivenDBInputSplit dataSplit =
081        (DataDrivenDBInputFormat.DataDrivenDBInputSplit) getSplit();
082    DBConfiguration dbConf = getDBConf();
083    String [] fieldNames = getFieldNames();
084    String tableName = getTableName();
085    String conditions = getConditions();
086
087    // Build the WHERE clauses associated with the data split first.
088    // We need them in both branches of this function.
089    StringBuilder conditionClauses = new StringBuilder();
090    conditionClauses.append("( ").append(dataSplit.getLowerClause());
091    conditionClauses.append(" ) AND ( ").append(dataSplit.getUpperClause());
092    conditionClauses.append(" )");
093
094    if(dbConf.getInputQuery() == null) {
095      // We need to generate the entire query.
096      query.append("SELECT ");
097
098      for (int i = 0; i < fieldNames.length; i++) {
099        query.append(fieldNames[i]);
100        if (i != fieldNames.length -1) {
101          query.append(", ");
102        }
103      }
104
105      query.append(" FROM ").append(tableName);
106      if (!dbProductName.startsWith("ORACLE")) {
107        // Seems to be necessary for hsqldb? Oracle explicitly does *not*
108        // use this clause.
109        query.append(" AS ").append(tableName);
110      }
111      query.append(" WHERE ");
112      if (conditions != null && conditions.length() > 0) {
113        // Put the user's conditions first.
114        query.append("( ").append(conditions).append(" ) AND ");
115      }
116
117      // Now append the conditions associated with our split.
118      query.append(conditionClauses.toString());
119
120    } else {
121      // User provided the query. We replace the special token with our WHERE clause.
122      String inputQuery = dbConf.getInputQuery();
123      if (inputQuery.indexOf(DataDrivenDBInputFormat.SUBSTITUTE_TOKEN) == -1) {
124        LOG.error("Could not find the clause substitution token "
125            + DataDrivenDBInputFormat.SUBSTITUTE_TOKEN + " in the query: ["
126            + inputQuery + "]. Parallel splits may not work correctly.");
127      }
128
129      query.append(inputQuery.replace(DataDrivenDBInputFormat.SUBSTITUTE_TOKEN,
130          conditionClauses.toString()));
131    }
132
133    LOG.debug("Using query: " + query.toString());
134
135    return query.toString();
136  }
137}