net.mooncloud.mapreduce.lib.db.OracleDBRecordReader.java Source code

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Here is the source code for net.mooncloud.mapreduce.lib.db.OracleDBRecordReader.java

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/**
 * 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 net.mooncloud.mapreduce.lib.db;

import java.io.IOException;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.SQLException;

import net.mooncloud.Record;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.mapreduce.lib.db.DBConfiguration;

/**
 * A RecordReader that reads records from an Oracle SQL table.
 */
@InterfaceAudience.Public
@InterfaceStability.Evolving
public class OracleDBRecordReader extends DBRecordReader {

    /** Configuration key to set to a timezone string. */
    public static final String SESSION_TIMEZONE_KEY = "oracle.sessionTimeZone";

    private static final Log LOG = LogFactory.getLog(OracleDBRecordReader.class);

    public OracleDBRecordReader(DBInputFormat.DBInputSplit split, Class<Record> inputClass, Configuration conf,
            Connection conn, DBConfiguration dbConfig, String cond, String[] fields, String table)
            throws SQLException {
        super(split, inputClass, conf, conn, dbConfig, cond, fields, table);
        setSessionTimeZone(conf, conn);
    }

    /** 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();
    }

    /**
     * Set session time zone
     * 
     * @param conf
     *            The current configuration. We read the
     *            'oracle.sessionTimeZone' property from here.
     * @param conn
     *            The connection to alter the timezone properties of.
     */
    public static void setSessionTimeZone(Configuration conf, Connection conn) throws SQLException {
        // need to use reflection to call the method setSessionTimeZone on
        // the OracleConnection class because oracle specific java libraries are
        // not accessible in this context.
        Method method;
        try {
            method = conn.getClass().getMethod("setSessionTimeZone", new Class[] { String.class });
        } catch (Exception ex) {
            LOG.error("Could not find method setSessionTimeZone in " + conn.getClass().getName(), ex);
            // rethrow SQLException
            throw new SQLException(ex);
        }

        // Need to set the time zone in order for Java
        // to correctly access the column "TIMESTAMP WITH LOCAL TIME ZONE".
        // We can't easily get the correct Oracle-specific timezone string
        // from Java; just let the user set the timezone in a property.
        String clientTimeZone = conf.get(SESSION_TIMEZONE_KEY, "GMT");
        try {
            method.setAccessible(true);
            method.invoke(conn, clientTimeZone);
            LOG.info("Time zone has been set to " + clientTimeZone);
        } catch (Exception ex) {
            LOG.warn("Time zone " + clientTimeZone + " could not be set on Oracle database.");
            LOG.warn("Setting default time zone: GMT");
            try {
                // "GMT" timezone is guaranteed to exist.
                method.invoke(conn, "GMT");
            } catch (Exception ex2) {
                LOG.error("Could not set time zone for oracle connection", ex2);
                // rethrow SQLException
                throw new SQLException(ex);
            }
        }
    }
}