| /** |
| * 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.io.IOException; |
| import java.sql.Connection; |
| import java.sql.ResultSet; |
| import java.sql.SQLException; |
| import java.sql.Statement; |
| |
| import org.apache.hadoop.conf.Configuration; |
| |
| /** |
| * A RecordReader that reads records from an Oracle SQL table. |
| */ |
| public class OracleDBRecordReader<T extends DBWritable> extends DBRecordReader<T> { |
| |
| public OracleDBRecordReader(DBInputFormat.DBInputSplit split, |
| Class<T> inputClass, Configuration conf, Connection conn, DBConfiguration dbConfig, |
| String cond, String [] fields, String table) throws SQLException { |
| super(split, inputClass, conf, conn, dbConfig, cond, fields, table); |
| } |
| |
| /** Returns the query for selecting the records from an Oracle DB. */ |
| protected String getSelectQuery() { |
| StringBuilder query = new StringBuilder(); |
| DBConfiguration dbConf = getDBConf(); |
| String conditions = getConditions(); |
| String tableName = getTableName(); |
| String [] fieldNames = getFieldNames(); |
| |
| // Oracle-specific codepath to use rownum instead of LIMIT/OFFSET. |
| if(dbConf.getInputQuery() == null) { |
| query.append("SELECT "); |
| |
| for (int i = 0; i < fieldNames.length; i++) { |
| query.append(fieldNames[i]); |
| if (i != fieldNames.length -1) { |
| query.append(", "); |
| } |
| } |
| |
| query.append(" FROM ").append(tableName); |
| if (conditions != null && conditions.length() > 0) |
| query.append(" WHERE ").append(conditions); |
| String orderBy = dbConf.getInputOrderBy(); |
| if (orderBy != null && orderBy.length() > 0) { |
| query.append(" ORDER BY ").append(orderBy); |
| } |
| } else { |
| //PREBUILT QUERY |
| query.append(dbConf.getInputQuery()); |
| } |
| |
| try { |
| DBInputFormat.DBInputSplit split = getSplit(); |
| if (split.getLength() > 0 && split.getStart() > 0){ |
| String querystring = query.toString(); |
| |
| query = new StringBuilder(); |
| query.append("SELECT * FROM (SELECT a.*,ROWNUM dbif_rno FROM ( "); |
| query.append(querystring); |
| query.append(" ) a WHERE rownum <= ").append(split.getStart()); |
| query.append(" + ").append(split.getLength()); |
| query.append(" ) WHERE dbif_rno >= ").append(split.getStart()); |
| } |
| } catch (IOException ex) { |
| // ignore, will not throw. |
| } |
| |
| return query.toString(); |
| } |
| } |