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https://issues.apache.org/jira/browse/PIG-4802?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15141476#comment-15141476
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Daniel Dai commented on PIG-4802:
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Want to add some clarity to the code:
1. factor *= DEFAULT_DISTINCT_FACTOR; => factor = DEFAULT_DISTINCT_FACTOR;
factor *= DEFAULT_AGGREGATION_FACTOR; => factor = DEFAULT_AGGREGATION_FACTOR;
2. Can we retain the simple version: getParallelismFactor(), the added
getParallelismFactor(TezOperator successor) only be used by
TezParallelismFactorVisitor. Also add a comment why the parameter is needed.
> Autoparallelism should estimate less when there is combiner
> -----------------------------------------------------------
>
> Key: PIG-4802
> URL: https://issues.apache.org/jira/browse/PIG-4802
> Project: Pig
> Issue Type: Improvement
> Reporter: Rohini Palaniswamy
> Assignee: Rohini Palaniswamy
> Fix For: 0.16.0
>
> Attachments: PIG-4802-1.patch
>
>
> When there is a combiner, it reduces records by a lot. Auto-parallelism
> should take that into account.
> Also currently we multiply by a factor of 10 if there is any FLATTEN. Users
> usually have FLATTEN(group) when the group by key is a compound key and it
> ends up estimating high. Only FLATTEN of bag should be considered.
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