玩转大数据系列之Apache Pig如何与MySQL集成（三）

上篇介绍了如何把Pig的结果存储到Solr中，那么可能就会有朋友问了，为什么不存到数据库呢？ 不支持还是？ 其实只要我们愿意，我们可以存储它的结果集到任何地方，只需要重写我们自己的StoreFunc类即可。

关于如何将Pig分析完的结果存储到数据库，在pig的piggy贡献组织里，已经有了对应的UDF了，piggybank是非apache官方提供的 工具 函数，里面的大部分的UDF都是，其他公司或着个人在后来使用时贡献的，这些工具类，虽然没有正式划入pig的源码包里，但是pig每次发行的时候，都会以扩展库的形式附带，编译后会放在pig根目录下一个叫contrib的目录下，

piggybank的地址是

https://cwiki.apache.org/confluence/display/PIG/PiggyBank

，感兴趣的朋友们，可以看一看。

将pig分析完的结果存入到数据库，也是非常简单的，需要的条件有：

（1）piggybank.jar的jar包

（2）依赖数据库的对应的驱动jar

有一点需要注意下，在将结果存储到数据库之前，一定要确保有访问和写入数据库的权限，否则任务就会失败！

散仙在存储到远程的 MySQL 上，就是由于权限的问题，而写入失败了，具体的异常是这样描述的：

Access denied for user 'root'@'localhost'

当出现上面异常的时候，就意味着权限写入有问题，我们使用以下的授权方法，来给目标机赋予权限：

（1）允许所有的机器ip访问

GRANT ALL PRIVILEGES ON *.* TO 'myuser'@'%' IDENTIFIED BY 'mypassword' WITH GRANT OPTION; 

（2）允许指定的机器ip访问：

1. GRANT ALL PRIVILEGES ON *.* TO 'myuser'@'192.168.1.3' IDENTIFIED BY    'mypassword' WITH GRANT OPTION;  

确定有权限之后，我们就可以造一份数据，测试是否可以将HDFS上的数据存储到数据库中，测试数据如下：

1,2,3
1,2,4
2,2,4
3,4,2
8,2,4

提前在对应的MySQL上，建库建表建字段，看下散仙测试表的结构：

最后，在来看下我们的pig脚本是如何定义和使用的：

--注册数据库驱动包和piggybank的jar
register ./dependfiles/mysql-connector-java-5.1.23-bin.jar;
register ./dependfiles/piggybank.jar

--为了能使schemal和数据库对应起来，建议在这个地方给数据加上列名
a = load '/tmp/dongliang/g.txt' using PigStorage(',') as (id:int,name:chararray,count:int) ;


--过滤出id大于2的数据

a = filter a by id > 2;

--存储结果到数据库里
STORE a INTO '/tmp/dbtest' using org.apache.pig.piggybank.storage.DBStorage('com.mysql.jdbc.Driver', 'jdbc:mysql://192.168.146.63/user', 'root', 'pwd',
    'INSERT into pig(id,name,count) values (?,?,?)');
~

执行成功后，我们再去查看数据库发现已经将pig处理后的数据正确的写入到了数据库中：

最后，附上DBStore类的源码：

/*
 * 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.pig.piggybank.storage;

import org.joda.time.DateTime;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.JobContext;
import org.apache.hadoop.mapreduce.OutputCommitter;
import org.apache.hadoop.mapreduce.OutputFormat;
import org.apache.hadoop.mapreduce.RecordWriter;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.pig.StoreFunc;
import org.apache.pig.backend.executionengine.ExecException;
import org.apache.pig.data.DataByteArray;
import org.apache.pig.data.DataType;
import org.apache.pig.data.Tuple;

import java.io.IOException;
import java.sql.*;

public class DBStorage extends StoreFunc {
  private final Log log = LogFactory.getLog(getClass());

  private PreparedStatement ps;
  private Connection con;
  private String jdbcURL;
  private String user;
  private String pass;
  private int batchSize;
  private int count = 0;
  private String insertQuery;

  public DBStorage(String driver, String jdbcURL, String insertQuery) {
    this(driver, jdbcURL, null, null, insertQuery, "100");
  }

  public DBStorage(String driver, String jdbcURL, String user, String pass,
      String insertQuery) throws SQLException {
    this(driver, jdbcURL, user, pass, insertQuery, "100");
  }

  public DBStorage(String driver, String jdbcURL, String user, String pass,
      String insertQuery, String batchSize) throws RuntimeException {
    log.debug("DBStorage(" + driver + "," + jdbcURL + "," + user + ",XXXX,"
        + insertQuery + ")");
    try {
      Class.forName(driver);
    } catch (ClassNotFoundException e) {
      log.error("can't load DB driver:" + driver, e);
      throw new RuntimeException("Can't load DB Driver", e);
    }
    this.jdbcURL = jdbcURL;
    this.user = user;
    this.pass = pass;
    this.insertQuery = insertQuery;
    this.batchSize = Integer.parseInt(batchSize);
  }

  /**
   * Write the tuple to Database directly here.
   */
  public void putNext(Tuple tuple) throws IOException {
    int sqlPos = 1;
    try {
      int size = tuple.size();
      for (int i = 0; i < size; i++) {
        try {
          Object field = tuple.get(i);

          switch (DataType.findType(field)) {
          case DataType.NULL:
            ps.setNull(sqlPos, java.sql.Types.VARCHAR);
            sqlPos++;
            break;

          case DataType.BOOLEAN:
            ps.setBoolean(sqlPos, (Boolean) field);
            sqlPos++;
            break;

          case DataType.INTEGER:
            ps.setInt(sqlPos, (Integer) field);
            sqlPos++;
            break;

          case DataType.LONG:
            ps.setLong(sqlPos, (Long) field);
            sqlPos++;
            break;

          case DataType.FLOAT:
            ps.setFloat(sqlPos, (Float) field);
            sqlPos++;
            break;

          case DataType.DOUBLE:
            ps.setDouble(sqlPos, (Double) field);
            sqlPos++;
            break;

          case DataType.DATETIME:
            ps.setDate(sqlPos, new Date(((DateTime) field).getMillis()));
            sqlPos++;
            break;

          case DataType.BYTEARRAY:
            byte[] b = ((DataByteArray) field).get();
            ps.setBytes(sqlPos, b);

            sqlPos++;
            break;
          case DataType.CHARARRAY:
            ps.setString(sqlPos, (String) field);
            sqlPos++;
            break;
          case DataType.BYTE:
            ps.setByte(sqlPos, (Byte) field);
            sqlPos++;
            break;

          case DataType.MAP:
          case DataType.TUPLE:
          case DataType.BAG:
            throw new RuntimeException("Cannot store a non-flat tuple "
                + "using DbStorage");

          default:
            throw new RuntimeException("Unknown datatype "
                + DataType.findType(field));

          }

        } catch (ExecException ee) {
          throw new RuntimeException(ee);
        }

      }
      ps.addBatch();
      count++;
      if (count > batchSize) {
        count = 0;
        ps.executeBatch();
        ps.clearBatch();
        ps.clearParameters();
      }
    } catch (SQLException e) {
      try {
        log
            .error("Unable to insert record:" + tuple.toDelimitedString("\t"),
                e);
      } catch (ExecException ee) {
        // do nothing
      }
      if (e.getErrorCode() == 1366) {
        // errors that come due to utf-8 character encoding
        // ignore these kind of errors TODO: Temporary fix - need to find a
        // better way of handling them in the argument statement itself
      } else {
        throw new RuntimeException("JDBC error", e);
      }
    }
  }

  class MyDBOutputFormat extends OutputFormat<NullWritable, NullWritable> {

    @Override
    public void checkOutputSpecs(JobContext context) throws IOException,
        InterruptedException {
      // IGNORE
    }

    @Override
    public OutputCommitter getOutputCommitter(TaskAttemptContext context)
        throws IOException, InterruptedException {
      return new OutputCommitter() {

        @Override
        public void abortTask(TaskAttemptContext context) throws IOException {
          try {
            if (ps != null) {
              ps.close();
            }
            if (con != null) {
              con.rollback();
              con.close();
            }
          } catch (SQLException sqe) {
            throw new IOException(sqe);
          }
        }

        @Override
        public void commitTask(TaskAttemptContext context) throws IOException {
          if (ps != null) {
            try {
              ps.executeBatch();
              con.commit();
              ps.close();
              con.close();
              ps = null;
              con = null;
            } catch (SQLException e) {
              log.error("ps.close", e);
              throw new IOException("JDBC Error", e);
            }
          }
        }

        @Override
        public boolean needsTaskCommit(TaskAttemptContext context)
            throws IOException {
          return true;
        }

        @Override
        public void cleanupJob(JobContext context) throws IOException {
          // IGNORE
        }

        @Override
        public void setupJob(JobContext context) throws IOException {
          // IGNORE
        }

        @Override
        public void setupTask(TaskAttemptContext context) throws IOException {
          // IGNORE
        }
      };
    }

    @Override
    public RecordWriter<NullWritable, NullWritable> getRecordWriter(
        TaskAttemptContext context) throws IOException, InterruptedException {
      // We don't use a record writer to write to database
    	return new RecordWriter<NullWritable, NullWritable>() {
    		   	  @Override
    		   	  public void close(TaskAttemptContext context) {
    		   		  // Noop
    		    	  }
    		    	  @Override
    		    	  public void write(NullWritable k, NullWritable v) {
    		    		  // Noop
    		    	  }
    		      };
    }

  }

  @SuppressWarnings("unchecked")
  @Override
  public OutputFormat getOutputFormat()
      throws IOException {
    return new MyDBOutputFormat();
  }

  /**
   * Initialise the database connection and prepared statement here.
   */
  @SuppressWarnings("unchecked")
  @Override
  public void prepareToWrite(RecordWriter writer)
      throws IOException {
    ps = null;
    con = null;
    if (insertQuery == null) {
      throw new IOException("SQL Insert command not specified");
    }
    try {
      if (user == null || pass == null) {
        con = DriverManager.getConnection(jdbcURL);
      } else {
        con = DriverManager.getConnection(jdbcURL, user, pass);
      }
      con.setAutoCommit(false);
      ps = con.prepareStatement(insertQuery);
    } catch (SQLException e) {
      log.error("Unable to connect to JDBC @" + jdbcURL);
      throw new IOException("JDBC Error", e);
    }
    count = 0;
  }

  @Override
  public void setStoreLocation(String location, Job job) throws IOException {
    // IGNORE since we are writing records to DB.
  }
}

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