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From jagatsi...@gmail.com
Subject RE: Calling one MR job within another MR job
Date Wed, 04 Apr 2012 12:47:08 GMT
Hello Stuti

 The way you have explained it seems we can think about caching the file2 already in nodes.

 -- Just out of context , In the same way replicated joins are being handled in Pig in which
one file (file2) to be joined is cached in the memory by file1.

 Regards

 Jagat

----- Original Message -----
From: Stuti Awasthi
Sent: 04/04/12 07:55 AM
To: mapreduce-user@hadoop.apache.org
Subject: RE: Calling one MR job within another MR job

Hi Ravi,
There is no job dependency so I cannot use chaining MR or JobControl as you suggested.
I have 2 relatively big files, I start processing with File1 as input to MR1 job , now this
processing required to find the data from File2. One way to do is loop through File2 and get
the data. Other way to pass File2 in MR2 job for parallel processing.
Second option is making hinting me to call an MR2 job inside from MR1 job. I am sure this
is the common problem that people usually face. What is the best way to resolve this kind
of issue.
Thanks

From: Ravi teja ch n v [mailto:raviteja.chnv@huawei.com]
 *Sent:* Wednesday, April 04, 2012 4:35 PM
 *To:* mapreduce-user@hadoop.apache.org
 *Subject:* RE: Calling one MR job within another MR job

Hi Stuti,
If you are looking for MRjob2 to run after MRjob1, ie the job dependency, 
you can use JobControl API, where you can manage the dependencies.
Calling another Job from a Mapper is not a good idea.
Thanks,
Ravi Teja

-----------------------------------------------------------------

From: Stuti Awasthi [stutiawasthi@hcl.com]
 *Sent:* 04 April 2012 16:04:19
 *To:* mapreduce-user@hadoop.apache.org
 *Subject:* Calling one MR job within another MR job

Hi all,
We have a usecase in which I start with first MR1 job with input file as File1.txt, and from
this job, call another MR2 job with input as File2.txt
So :
MRjob1{
Map(){
MRJob2(File2.txt)
}
}
MRJob2{
Processing….
}
My queries are is this kind of approach is possible and how much are the implications from
the performance perspective.
Regards,
Stuti Awasthi
HCL Comnet Systems and Services Ltd
F-8/9 Basement, Sec-3,Noida.

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