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https://issues.apache.org/jira/browse/PIG-1144?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Daniel Dai updated PIG-1144:
----------------------------

    Attachment: PIG-1144-2.patch

I think the reason is quantile job need to know how many reducers we are going 
to use in order to decide tuples to write into quantilesFile. The number of 
reducers is a constant field of the plan. We cannot say -1 and let hadoop to 
decide the parallelism later. The fix actually take default_parallel as the 
constant if user do not use PARALLEL key word. It applies to both order by and 
skew join. Merge join and FRJoin are map only and regular join has been taken 
care of in the original code. Attach the patch again, nothing change except for 
including a new test case for skew join.

> set default_parallelism construct does not set the number of reducers 
> correctly
> -------------------------------------------------------------------------------
>
>                 Key: PIG-1144
>                 URL: https://issues.apache.org/jira/browse/PIG-1144
>             Project: Pig
>          Issue Type: Bug
>          Components: impl
>    Affects Versions: 0.6.0
>         Environment: Hadoop 20 cluster with multi-node installation
>            Reporter: Viraj Bhat
>            Assignee: Daniel Dai
>             Fix For: 0.7.0
>
>         Attachments: brokenparallel.out, genericscript_broken_parallel.pig, 
> PIG-1144-1.patch, PIG-1144-2.patch
>
>
> Hi all,
>  I have a Pig script where I set the parallelism using the following set 
> construct: "set default_parallel 100" . I modified the "MRPrinter.java" to 
> printout the parallelism
> {code}
> ...
> public void visitMROp(MapReduceOper mr)
> mStream.println("MapReduce node " + mr.getOperatorKey().toString() + " 
> Parallelism " + mr.getRequestedParallelism());
> ...
> {code}
> When I run an explain on the script, I see that the last job which does the 
> actual sort, runs as a single reducer job. This can be corrected, by adding 
> the PARALLEL keyword in front of the ORDER BY.
> Attaching the script and the explain output
> Viraj

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