The "Partitioner" implementation used with your job should define which
reduce target receives a given map output key.
I don't know if an existing Partitioner implementation exists which
meets your needs, but it's not a very complex interface to develop, if
nothing existing works for you.
Brad
On 10/18/2010 04:43 PM, Shi Yu wrote:
How many tags you have? If you have several number of tags, you'd
better create a Vector class to hold those tags. And define sum
function to increment the values of tags. Then the value class should
be your new Vector class. That's better and more decent than the
Textpair approach.
Shi
On 2010-10-18 5:19, Matthew John wrote:
Hi all,
I had a small doubt regarding the reduce module. What I understand is
that
after the shuffle / sort phase , all the records with the same key value
goes into a reduce function. If thats the case, what is the attribute
of the
Writable key which ensures that all the keys go to the same reduce ?
I am working on a reduce side Join where I need to tag all the keys
with a
bit which might vary but still want all those records to go into same
reduce. In Hadoop the Definitive Guide, pg. 235 they are using
TextPair for
the key. But I dont understand how the keys with different tag
information
goes into the same reduce.
Matthew
