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https://issues.apache.org/jira/browse/HADOOP-3306?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12600481#action_12600481
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Peeyush Bishnoi commented on HADOOP-3306:
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This issue is somewhat similar to the issue HADOOP-2876
> streaming should default to KeyValueTextInputFormat with IdentityMapper
> -----------------------------------------------------------------------
>
> Key: HADOOP-3306
> URL: https://issues.apache.org/jira/browse/HADOOP-3306
> Project: Hadoop Core
> Issue Type: Improvement
> Components: contrib/streaming
> Affects Versions: 0.15.3
> Reporter: Joydeep Sen Sarma
> Priority: Minor
>
> in 15.3 - streaming defaults to TextInputFormat (without -inputformat option).
> this is great in case the PipeMapper is used. but in many cases people want
> to do an IdentityMapper - and it fails with the IdentityMapper:
> a) the map output key type becomes LongWritable (but hadoop has already
> defaulted to expect Text)
> b) the map output key is the Line number - and intuitively - this is not what
> the user expects (almost no one wants to use the line number as the map key).
> if we could simply default to KeyValueTextInputFormat with IdentityMapper -
> that would resolve both of these problems. This would change default behavior
> though - so a little leery ..
> using '-mapper cat' is the common workaround - but it just seems like a
> needless waste of resources ..
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