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https://issues.apache.org/jira/browse/HIVE-17486?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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liyunzhang updated HIVE-17486:
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Attachment: explain.28.scan.share.false
explain.28.scan.share.true
I set the flag {{hive.spark.optimize.shared.work}} to enable the
SharedWorkOptimizer in Hive on Spark. The attach explain.28.scan.share.true is
the explain when enabling the flag and explain.28.scan.share.false is the
explain when disabling the flag for
[DS/query28.sql|https://github.com/kellyzly/hive-testbench/blob/hive14/sample-queries-tpcds/query28.sql]
> Enable SharedWorkOptimizer in tez on HOS
> ----------------------------------------
>
> Key: HIVE-17486
> URL: https://issues.apache.org/jira/browse/HIVE-17486
> Project: Hive
> Issue Type: Bug
> Reporter: liyunzhang
> Assignee: liyunzhang
> Attachments: explain.28.scan.share.false, explain.28.scan.share.true,
> scanshare.after.svg, scanshare.before.svg
>
>
> in HIVE-16602, Implement shared scans with Tez.
> Given a query plan, the goal is to identify scans on input tables that can be
> merged so the data is read only once. Optimization will be carried out at the
> physical level. In Hive on Spark, it caches the result of spark work if the
> spark work is used by more than 1 child spark work. After sharedWorkOptimizer
> is enabled in physical plan in HoS, the identical table scans are merged to 1
> table scan. This result of table scan will be used by more 1 child spark
> work. Thus we need not do the same computation because of cache mechanism.
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