Jeff Zhang commented on PIG-16:

I looks like this item has already been fixed in PIG-895

> setting parallel from grunt via set command
> -------------------------------------------
>                 Key: PIG-16
>                 URL: https://issues.apache.org/jira/browse/PIG-16
>             Project: Pig
>          Issue Type: Improvement
>          Components: grunt
>            Reporter: Olga Natkovich
>            Priority: Minor
> I'd like to propose a different model which uses the grunt "set" option 
> and/or a command line option which sets reduce
> parallelism to the be true and automatic.
>       set reduce_parallelism TRUE
>       set reduce_parallelism FALSE [Default - BTW, why is this the default?]
> This way I won't have to update my script every single time I try playing 
> with -D"hod=-m N", parallelism for reduce
> statements will default, appropriately, to 2*(N-1).
> Alternatively, could I just specify PARALLEL with no value or PARALLEL 
> DEFAULT;  And any time I needed to force reduce
> to be single job, I could write PARALLEL 1.
> Basically, this whole thing tripped me up for a long time and I just haven't 
> understood if there is a really good
> reason to not make parallelism.
> I guess it might be if you have aggregation functions that do not parallelize.
> If this is the case, then it seems to me that this should be detectable 
> automagically based on whether the function is
> a vanilla EvalFunction or if it is an AlgebraicFunction.

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