[HADOOP-2806] Streaming has no way to force entire record (or null) as key

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 0.17.0
• Assignee: Amareshwari Sriramadasu
• Reporter: Marco Nicosia
• Created: 10/Feb/08 01:02
• Updated: 08/Jul/09 17:05
• Resolved: 17/Mar/08 05:45

Description

I think perhaps streaming needs a "-allkey" or "-nullkey" option? Otherwise, I'm concerned there is a subtle streaming documentation problem.

These two docs:

http://hadoop.apache.org/core/docs/current/streaming.html
http://wiki.apache.org/hadoop/HadoopStreaming (Should be merged with above?)

... seem to ignore that streaming, by default, splits key/value on TAB. Sure, they mention it, but in all the simple (no separator) examples, they don't seem to take into account that streaming may inconsistently decide whether the whole line is the key, or just up to the first tab, should one occur. This means that some records might be sorted differently as compared to others based on whether or not there's a tab?

Here's a very simple pair of examples, that to the naive, should produce the same output, but do not:

> [hod] (marco) >> run dfs -fs local -cat str-tabs
> a 1
> b 3
> a 4
>
> [hod] (marco) >> run dfs -put str-tabs str-tabs
>
> [hod] (marco) >> run jar hadoop-streaming.jar -input str-tabs -output str-tabs.out -mapper /bin/cat -reducer /bin/cat
> [blah blah blah]
>
> [hod] (marco) >> run dfs -cat str-tabs.out/part-00000
> a 4
> a 1
> b 3

Compare to this negative-test:
> [hod] (marco) >> run dfs -fs local -cat str-notabs
> a 1
> b 3
> a 4
>
> [hod] (marco) >> run dfs -put str-notabs str-notabs
>
> [hod] (marco) >> run jar hadoop-streaming.jar -input str-notabs -output str-notabs.out -mapper /bin/cat -reducer /bin/cat
> [blah blah blah]
>
> [hod] (marco) >> run dfs -cat str-notabs.out/part-00000
> a 1
> a 4
> b 3
>