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
019 package org.apache.hadoop.mapreduce.lib.db;
020
021 import java.io.DataInput;
022 import java.io.DataOutput;
023 import java.io.IOException;
024 import java.sql.Connection;
025 import java.sql.DatabaseMetaData;
026 import java.sql.PreparedStatement;
027 import java.sql.ResultSet;
028 import java.sql.SQLException;
029 import java.sql.Statement;
030 import java.util.ArrayList;
031 import java.util.List;
032
033 import org.apache.commons.logging.Log;
034 import org.apache.commons.logging.LogFactory;
035 import org.apache.hadoop.io.LongWritable;
036 import org.apache.hadoop.io.Writable;
037 import org.apache.hadoop.mapreduce.InputFormat;
038 import org.apache.hadoop.mapreduce.InputSplit;
039 import org.apache.hadoop.mapreduce.Job;
040 import org.apache.hadoop.mapreduce.JobContext;
041 import org.apache.hadoop.mapreduce.RecordReader;
042 import org.apache.hadoop.mapreduce.TaskAttemptContext;
043 import org.apache.hadoop.util.ReflectionUtils;
044 import org.apache.hadoop.classification.InterfaceAudience;
045 import org.apache.hadoop.classification.InterfaceStability;
046 import org.apache.hadoop.conf.Configurable;
047 import 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
057 public 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 }