Created: (HADOOP-1981) Need to document the controls for sorting and grouping into the reduce

Need to document the controls for sorting and grouping into
the reduce
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                 Key: HADOOP-1981
                 URL: htt
ps://issues.apache.org/jira/browse/HADOOP-1981
             Project: Hadoop
          Issue Type: Task
          Components: mapred
            Reporter: Owen O'Malley
            Assignee: Owen O'Malley
             Fix For: 0.15.0


The JavaDoc for the Reducer should document how to control
the sort order of keys and values via the JobConf methods:


  setOutputKeyComparatorClass
  setOutputValueGroupingComparator


Both methods desperately need better names. (I'd vote for
setKeySortingComparator and setKeyGroupingComparator.)

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Arun C Murthy reassigned HADOOP-1981:
-------------------------------------

    Assignee: Arun C Murthy  (was: Owen O'Malley)

> Need to document the controls for sorting and grouping
into the reduce
>
------------------------------------------------------------
----------
>
>                 Key: HADOOP-1981
>                 URL: htt
ps://issues.apache.org/jira/browse/HADOOP-1981
>             Project: Hadoop
>          Issue Type: Task
>          Components: mapred
>            Reporter: Owen O'Malley
>            Assignee: Arun C Murthy
>
> The JavaDoc for the Reducer should document how to
control the sort order of keys and values via the JobConf
methods:
> 
>   setOutputKeyComparatorClass
>   setOutputValueGroupingComparator
> 
> Both methods desperately need better names. (I'd vote
for setKeySortingComparator and setKeyGroupingComparator.)

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Arun C Murthy commented on HADOOP-1981:
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bq. Both methods desperately need better names. 

+1

I completely agree, unless anyone objects I'll roll this
into HADOOP-2046 since the changed names better reflect what
they are meant to do.

Oh, btw I'd go for {} and
{}... *smile*

> Need to document the controls for sorting and grouping
into the reduce
>
------------------------------------------------------------
----------
>
>                 Key: HADOOP-1981
>                 URL: htt
ps://issues.apache.org/jira/browse/HADOOP-1981
>             Project: Hadoop
>          Issue Type: Task
>          Components: mapred
>            Reporter: Owen O'Malley
>            Assignee: Arun C Murthy
>
> The JavaDoc for the Reducer should document how to
control the sort order of keys and values via the JobConf
methods:
> 
>   setOutputKeyComparatorClass
>   setOutputValueGroupingComparator
> 
> Both methods desperately need better names. (I'd vote
for setKeySortingComparator and setKeyGroupingComparator.)

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/HADOOP-1981?page=com.atlassian.jira.plugin.system.issuetabp
anels:comment-tabpanel#action_12537052 ] 

Doug Cutting commented on HADOOP-1981:
--------------------------------------

I'd rather keep this separate from HADOOP-2046, since it not
just documentation, but an incompatible code change.

As for names, I still like having 'output' in them, to
remove potential confusion with join-like stuff that
operates on inputs.  We probably don't need 'key' in their
name, since only keys are comparable anyway.  So I'd vote
for outputSortComparator and outputGroupComparator.  Perhaps
in HADOOP-2046 we should document "grouping" as a
primary mapreduce pipeline stage: map, (combine), sort,
group, reduce?


> Need to document the controls for sorting and grouping
into the reduce
>
------------------------------------------------------------
----------
>
>                 Key: HADOOP-1981
>                 URL: htt
ps://issues.apache.org/jira/browse/HADOOP-1981
>             Project: Hadoop
>          Issue Type: Task
>          Components: mapred
>            Reporter: Owen O'Malley
>            Assignee: Arun C Murthy
>
> The JavaDoc for the Reducer should document how to
control the sort order of keys and values via the JobConf
methods:
> 
>   setOutputKeyComparatorClass
>   setOutputValueGroupingComparator
> 
> Both methods desperately need better names. (I'd vote
for setKeySortingComparator and setKeyGroupingComparator.)

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