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https://issues.apache.org/jira/browse/PIG-3555?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Cheolsoo Park updated PIG-3555:
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Attachment: PIG-3555-4.patch
There was a mistake in the previous patch. Re-attaching a good one.
> Initial implementation of combiner optimization
> -----------------------------------------------
>
> Key: PIG-3555
> URL: https://issues.apache.org/jira/browse/PIG-3555
> Project: Pig
> Issue Type: Sub-task
> Components: tez
> Affects Versions: tez-branch
> Reporter: Cheolsoo Park
> Assignee: Cheolsoo Park
> Fix For: tez-branch
>
> Attachments: PIG-3555-1.patch, PIG-3555-2.patch, PIG-3555-3.patch,
> PIG-3555-4.patch
>
>
> To support algebraic UDFs and others, combiner is required. To start with, I
> am proposing the following initial implementation-
> * In Tez, combiner runs as part of ShuffledMergedInput in edges, so multiple
> combine plans (one per edge) need to be registered in a destination vertex.
> Each vertex is mapped to a TezOperator in Tez plan, so an array of combine
> plans will be stored in the TezOperator that maps to a destination vertex.
> * To register combine plans in a TezOperator, we will run a CombinerOptimizer
> on the Tez plan after TezCompiler generates it but before TezDagBuilder
> converts it into DAG.
> * Finally, TezDagBuilder will insert combine plans into the payload of
> ShuffledMergedInput while constructing a destination vertex.
> This initial implementation will allow us to run algebraic UDFs. In the
> future, we can implement more optimizations for limit, order-by, etc on top
> of this.
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