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From "Kartashov, Andy" <Andy.Kartas...@mpac.ca>
Subject using sequencefile generated by Sqoop in Mapreduce
Date Tue, 09 Oct 2012 17:18:47 GMT
Guys,

I have trouble using sequence file  in Mar-Reduce.  The output I get is very last record.

I am creating sequence file while importing MySQL table into Hadoop using:
$Sqoop import...... --as-sequencefile

I am then are trying to read from this file into the mapper and create keys from object's
Ids and values - the actual objects with attributes per each table's record.
In the Reducer I am iterating those objects and outputting objects's attributes to a .txt
file.

My Mapreduce code:

     public static void main(String[] args) throws Exception {
    ...
    conf.setOutputKeyClass(Text.class); // this will be one of the fields of the exported
table, say ids
   conf.setOutputValueClass(<Sqoop_class.class>); //say Sqoop_class.class generated_class_during_import
  conf.setInputFormat(SequenceFileInputFormat.class);
  conf.setOutputFormat(NullOutputFormat.class); // output will be to a .txt file
..


//====================================================================================================================
public static class MyMapper extends MapReduceBase implements Mapper<LongWritable, Sqoop_class,
Text, Sqoop_class> {
//--------------------------------------------------------------------------------------------------------------------
public void map(LongWritable key, Sqoop_class value, OutputCollector<Text, Sqoop_class>
output, Reporter reporter) throws IOException {
        output.collect(new Text(value.get_foo_id ().toString()), value);
     } // end of map()
} // end of static class MyMapper



//====================================================================================================================
  public static class MyReducer extends MapReduceBase implements Reducer<Text, Sqoop_class,
Text, Sqoop_class> {

//--------------------------------------------------------------------------------------------------------------------
   public void reduce(Text key, Iterator<Sqoop_class> values, OutputCollector<Text,
Sqoop_class> output, Reporter reporter) throws IOException {
  .......
  while (values.hasNext()){
       output.collect(key,epa); //output is to Null...
       out.writeBytes(" values.next().get_foo_name() + "!\n "  );
       } // end of while loop
            ......
        }//end of reduce()
} // end of static class MyReducer

Would not Mapper create Keys from each Sqoop_class id value and Values will be instance of
each Sqoop_class
Then we group those instances in the reducer and Iterate through them retrieving attribute
names from each object.
Somehow the values of one last instance of the object is only written.

Should not conf.setInputFormat(SequenceFileInputFormat.class);
And
Sqoop_class.class work together reading from Sequence file?

Thanks,
Andy
From: nagarjuna kanamarlapudi [mailto:nagarjuna.kanamarlapudi@gmail.com]
Sent: Tuesday, October 09, 2012 11:03 AM
To: user@hadoop.apache.org
Subject: Re: Hive-Site XML changing any proprty.

by restarting the hive server your problem should be solved.

Not sure if we have any other ways of starting the hive server other than .


1. bin/hive --service hiveserver

2. HIVE_PORT=xxxx ./hive --service hiveserver


Regards,
Nagarjuna

On Tue, Oct 9, 2012 at 8:10 PM, Uddipan Mukherjee <Uddipan_Mukherjee@infosys.com<mailto:Uddipan_Mukherjee@infosys.com>>
wrote:
Hi hadoop, hive gurus,

    I have a requirement to change the path of the scratch folder of Hive.  Hence I have added
following property in Hive-Site.xml and changed its value as required.

<property>
  <name>hive.exec.scratchdir</name>
  <value/tmp/example</value>
  <description>Scratch space for Hive jobs</description>
</property>

But still it is not reflecting as required. Do I need to restart Hive server to read the updated
value in the file.

Also is there any other way other than restarting Hive server?

Any pointers will be helpful.

Thanks And Regards
Uddipan Mukherjee


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