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Hadoop >> mail # user >> probably very stupid question


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jamal sasha 2013-01-14, 23:44
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Re: probably very stupid question
Hi Jamal

I believe a reduce side join is what you are looking for.

You can use MultipleInputs and achieve a reduce side join to achieve this.

http://kickstarthadoop.blogspot.com/2011/09/joins-with-plain-map-reduce.html

Regards
Bejoy KS

Sent from remote device, Please excuse typos

-----Original Message-----
From: jamal sasha <[EMAIL PROTECTED]>
Date: Mon, 14 Jan 2013 15:44:25
To: [EMAIL PROTECTED]<[EMAIL PROTECTED]>
Reply-To: [EMAIL PROTECTED]
Subject: probably very stupid question

Hi,
  Probably a very lame question.
I have two documents and I want to find the overlap of both documents in
map reduce fashion and then compare the overlap (lets say I have some
measure to do that)

SO this is what I am thinking:

    1) Run the normal wordcount job on one document (
https://sites.google.com/site/hadoopandhive/home/hadoop-how-to-count-number-of-times-a-word-appeared-in-a-file-using-map-reduce-framework
)
    2) But rather than saving a file, save everything in a
HashMap(word,true)
    3) Pass that HashMap along the second wordcount mapreduce program and
then as I am processing the second document, check the words against the
HashMap to find whether the word is present or not.

So, something like this

     1) HashMap<String, boolean> hm = runStepOne(); <-- map reduce job
     2) runSteptwo(HashMap<String, boolean>)
How do I do this in hadoop
I know there can be some other hacks but what I am trying to achieve is get
comfortable with the java framework..
So, from the above link.. how do i save the datastrcuture instead of file.
How do I pass the datastructure as an argument?