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.sql.Connection;
022    import java.sql.ResultSet;
023    import java.sql.PreparedStatement;
024    import java.sql.SQLException;
025    
026    import org.apache.hadoop.classification.InterfaceAudience;
027    import org.apache.hadoop.classification.InterfaceStability;
028    import org.apache.hadoop.conf.Configuration;
029    
030    /**
031     * A RecordReader that reads records from a MySQL table.
032     */
033    @InterfaceAudience.Public
034    @InterfaceStability.Evolving
035    public class MySQLDBRecordReader<T extends DBWritable> extends DBRecordReader<T> {
036    
037      public MySQLDBRecordReader(DBInputFormat.DBInputSplit split, 
038          Class<T> inputClass, Configuration conf, Connection conn, DBConfiguration dbConfig,
039          String cond, String [] fields, String table) throws SQLException {
040        super(split, inputClass, conf, conn, dbConfig, cond, fields, table);
041      }
042    
043      // Execute statements for mysql in unbuffered mode.
044      protected ResultSet executeQuery(String query) throws SQLException {
045        statement = getConnection().prepareStatement(query,
046          ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_READ_ONLY);
047        statement.setFetchSize(Integer.MIN_VALUE); // MySQL: read row-at-a-time.
048        return statement.executeQuery();
049      }
050    }