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From "Olga Natkovich (JIRA)" <j...@apache.org>
Subject [jira] Commented: (PIG-539) unable to control parallelism of Map tasks
Date Thu, 20 Nov 2008 18:40:44 GMT

    [ https://issues.apache.org/jira/browse/PIG-539?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12649442#action_12649442

Olga Natkovich commented on PIG-539:


I don't disagree with you. I am just saying that at this point, this is not  abug, but a feature
that breaks backward compatibility. If you feel strongly that this is something that we need
to do, please, post your proposal to pig-user list so that others can comment on it. Also,
there might be other ways, not just using parallel that might address your problem.

> unable to control parallelism of Map tasks
> ------------------------------------------
>                 Key: PIG-539
>                 URL: https://issues.apache.org/jira/browse/PIG-539
>             Project: Pig
>          Issue Type: Bug
>          Components: impl
>         Environment: local execution + hadoop execution
>            Reporter: Christopher Olston
> I put "PARALLEL 1" following *every* statement in my pig script, and it still executes
maps with more than 1 parallel task. This is a major problem because for one of my operations
I need to have a serialized (non-parallel) map.
> Probably the semantics of parallelism should be as follows:
>  1. group pig operators into map/reduce stages
>  2. for each stage, take the minimum of the "Parallel" directives given by the user for
statements executed as part of that stage
> (We'll have to decide on a rule for statements that use the combiner, which execute partially
on the map side and partially on the reduce side ...)

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