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https://issues.apache.org/jira/browse/HIVE-3652?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13577403#comment-13577403
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Amareshwari Sriramadasu commented on HIVE-3652:
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Seems I figured it out. The hive.auto.convert.join.noconditionaltask.size is
not the number of rows. When i changed
hive.auto.convert.join.noconditionaltask.size value in the attached tests, it
is launching one MR job. Will upload the patch again to add tests.
> Join optimization for star schema
> ---------------------------------
>
> Key: HIVE-3652
> URL: https://issues.apache.org/jira/browse/HIVE-3652
> Project: Hive
> Issue Type: Improvement
> Components: Query Processor
> Reporter: Amareshwari Sriramadasu
> Assignee: Vikram Dixit K
> Fix For: 0.11.0
>
> Attachments: HIVE-3652-tests.patch
>
>
> Currently, if we join one fact table with multiple dimension tables, it
> results in multiple mapreduce jobs for each join with dimension table,
> because join would be on different keys for each dimension.
> Usually all the dimension tables will be small and can fit into memory and so
> map-side join can used to join with fact table.
> In this issue I want to look at optimizing such query to generate single
> mapreduce job sothat mapper loads dimension tables into memory and joins with
> fact table on different keys as well.
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