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From Mark Vigeant <mark.vige...@riskmetrics.com>
Subject RE: Multiple Input Paths
Date Wed, 04 Nov 2009 16:07:57 GMT

That sounds so awesome! Yeah I wish I had that class now. Do you have any tips on how to create
such a delegating class? The best I can come up with is to just submit both files to the mapper
using multiple input paths and then having anif statement at the beginning of the map that
checks which file it's dealing with but I'm skeptical that I can even make that work... Is
there a way you know of that I could submit 2 mapper classes to the job?

-----Original Message-----
From: Amogh Vasekar [mailto:amogh@yahoo-inc.com] 
Sent: Wednesday, November 04, 2009 1:50 AM
To: common-user@hadoop.apache.org
Subject: Re: Multiple Input Paths

Hi Mark,
A future release of Hadoop will have a MultipleInputs class, akin to MultipleOutputs. This
would allow you to have a different inputformat, mapper depending on the path you are getting
the split from. It uses special Delegating[mapper/input] classes to resolve this. I understand
backporting this is more or less out of question, but the ideas there might provide pointers
to help you solve your current problem.
Just a thought :)


On 11/3/09 8:44 PM, "Mark Vigeant" <mark.vigeant@riskmetrics.com> wrote:

Hey Vipul

No I haven't concatenated my files yet, and I was just thinking over how to approach the issue
of multiple input paths.

I actually did what Amandeep hinted at which was we wrote our own XMLInputFormat and XMLRecordReader.
When configuring the job in my driver I set job.setInputFormatClass(XMLFileInputFormat.class)
and what it does is send chunks of XML to the mapper as opposed to lines of text or whole
files. So I specified the Line Delimiter in the XMLRecordReader (ie <startTag>) and
everything in between the tags <startTag> and </startTag> are sent to the mapper.
Inside the map function is where to parse the data and write it to the table.

What I have to do now is just figure out how to set the Line Delimiter to be something common
in both XML files I'm reading. Currently I have 2 mapper classes and thus 2 submitted jobs
which is really inefficient and time consuming.

Make sense at all? Sorry if it doesn't, feel free to ask more questions


-----Original Message-----
From: Vipul Sharma [mailto:sharmavipul@gmail.com]
Sent: Monday, November 02, 2009 7:48 PM
To: common-user@hadoop.apache.org
Subject: RE: Multiple Input Paths


were you able to concatenate both the xml files together. What did you do to
keep the resulting xml well forned?

Vipul Sharma,
Cell: 281-217-0761

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