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https://issues.apache.org/jira/browse/PIG-2779?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13422762#comment-13422762
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Jie Li commented on PIG-2779:
-----------------------------
estimatedParallelism is a good one to add and these names look good to me. Has
default parallel already shown up in the job conf? For
pig.info.reducers.runtime.parallel, it should be same as mapred.reduce.tasks,
so do we still need it?
> Refactoring the code for setting number of reducers
> ---------------------------------------------------
>
> Key: PIG-2779
> URL: https://issues.apache.org/jira/browse/PIG-2779
> Project: Pig
> Issue Type: Bug
> Reporter: Jie Li
> Assignee: Jie Li
> Fix For: 0.11
>
> Attachments: PIG-2779.0.patch, PIG-2779.1.patch, PIG-2779.2.patch,
> TestNumberOfReducers.java, TestNumberOfReducers.java
>
>
> As PIG-2652 observed, currently the code for setting number of reducers is a
> little messy. MapReduceOper.requestedParallelism seems being misused in some
> plases, and now we support runtime estimation of #reducer which further
> complicates the problem.
> For example, if we specify parallel 1 for the order-by, the estimated
> #reducer will be used. If we specify parallel 2 while it estimates 4,
> order-by will fail due to "Illegal partition for Null". If we specify
> parallel 4 while it estimates 2, then some reducers will have nothing to do.
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