co.nubetech.apache.hadoop.mapred.DBQueryRecordReader.java Source code

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Here is the source code for co.nubetech.apache.hadoop.mapred.DBQueryRecordReader.java

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/**
 * Copyright 2010 Nube Technologies
 * 
 * Licensed 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 co.nubetech.apache.hadoop.mapred;

import java.io.IOException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.mapreduce.lib.db.DBConfiguration;
import org.apache.hadoop.mapreduce.lib.db.DataDrivenDBRecordReader;
import org.apache.log4j.Logger;

import co.nubetech.hiho.mapreduce.lib.db.ColumnInfo;
import co.nubetech.hiho.mapreduce.lib.db.GenericDBWritable;

public class DBQueryRecordReader extends DataDrivenDBRecordReader<GenericDBWritable> {

    final static Logger logger = Logger.getLogger(co.nubetech.hiho.mapreduce.lib.db.DBQueryRecordReader.class);

    protected ArrayList params;
    private LongWritable key = null;

    private GenericDBWritable value = null;
    private ArrayList<ColumnInfo> info;
    private ResultSet results;
    private long pos = 0;

    public ArrayList getParams() {
        return params;
    }

    public void setParams(ArrayList params) {
        this.params = params;
    }

    public DBQueryRecordReader(org.apache.hadoop.mapreduce.lib.db.DBInputFormat.DBInputSplit split,
            Configuration conf, Connection conn, DBConfiguration dbConfig, String cond, String[] fields,
            String table, String dbProduct, ArrayList params) throws SQLException {
        super(split, GenericDBWritable.class, conf, conn, dbConfig, cond, fields, table, dbProduct);
        this.params = params;
    }

    protected ResultSet executeQuery(String query) throws SQLException {
        this.statement = getConnection().prepareStatement(query, ResultSet.TYPE_FORWARD_ONLY,
                ResultSet.CONCUR_READ_ONLY);
        if (params != null) {
            logger.debug("Params are to be set");
            for (int i = 0; i < params.size(); ++i) {
                statement.setObject(i + 1, params.get(i));
                logger.debug("set i " + i + " " + params.get(i));
            }
        }

        return statement.executeQuery();

    }

    /** {@inheritDoc} */
    public LongWritable getCurrentKey() {
        return key;
    }

    /** {@inheritDoc} */
    public GenericDBWritable getCurrentValue() {
        return value;
    }

    /**
       * @deprecated Use {@link #nextKeyValue()}
       */
    @Deprecated
    public boolean next(LongWritable key, GenericDBWritable value) throws IOException {
        this.key = key;
        this.value = value;
        return nextKeyValue();
    }

    /** {@inheritDoc} */
    public boolean nextKeyValue() throws IOException {
        try {
            if (key == null) {
                key = new LongWritable();
            }
            if (value == null) {
                value = new GenericDBWritable();
            }
            if (null == this.results) {
                // First time into this method, run the query.
                this.results = executeQuery(getSelectQuery());
                info = GenericDBWritable.populateColumnInfo(results.getMetaData());
                logger.debug("Info is " + info);
            }
            if (!results.next()) {
                logger.debug("No results found ");
                return false;
            }
            // Set the key field value as the output key value
            key.set(pos + getSplit().getStart());
            value.setColumns(info);
            value.readFields(results);
            logger.debug("Set key, value");
            pos++;
        } catch (SQLException e) {
            throw new IOException("SQLException in nextKeyValue", e);
        }
        return true;
    }

}