[
https://issues.apache.org/jira/browse/HADOOP-4251?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12633939#action_12633939
]
Owen O'Malley commented on HADOOP-4251:
---------------------------------------
I believe that check was put in because it used to fail if the number of maps
was 0. Obviously, if you take out the check, you had better add a test case of
both reduces != 0 and reduces = 0 when maps = 0.
That said, it is probably better to run the reduces with no input than the
current behavior, which tends to surprise users.
> The reducer output is not created if the mapper input is empty
> --------------------------------------------------------------
>
> Key: HADOOP-4251
> URL: https://issues.apache.org/jira/browse/HADOOP-4251
> Project: Hadoop Core
> Issue Type: Bug
> Components: mapred
> Reporter: Namit Jain
> Assignee: Namit Jain
>
> For some Hive stuff, I ran into the following scenario:
> For a given map-reduce job, the input was empty. Because of that no mappers
> and reducers were created. It would have been helpful if an empty output for
> the reducer would have been created.
> After browsing though the code, it seems that in initTasks() in
> JobInProgress, no mappers and reducers are initialized if input is empty.
> I was thinking of putting a fix there. If the input is empty, before
> returning, create the output directory (as specified by the reducer) if
> needed.Any comments/suggestions....
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
