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https://issues.apache.org/jira/browse/HIVE-28490?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17893445#comment-17893445
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Denys Kuzmenko commented on HIVE-28490:
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Hi [~seonggon], I am a bit confused with the explanation on a slides.
{code}
For each DPP source, the removal is done in 3 steps:
1. Compute the discardable input operators of discarded TS.
{code}
however than on a next slide
{code}
We are going to remove TS_3 and retain TS_41.
discardableInputOps of TS_41:
{SEL_140, GBY_141, RS_142, GBY_143, RS_144}
{code}
aren't we. discarding TS_3?
> SharedWorkOptimizer sometimes removes useful DPP sources.
> ---------------------------------------------------------
>
> Key: HIVE-28490
> URL: https://issues.apache.org/jira/browse/HIVE-28490
> Project: Hive
> Issue Type: Improvement
> Reporter: Seonggon Namgung
> Assignee: Seonggon Namgung
> Priority: Major
> Labels: pull-request-available
> Attachments: 3.StopRemovingRetainableDPP.pptx
>
>
> Current SharedWorkOptimizer sometimes removes DPP sources that are not
> invalidated. I found that findAscendantWorkOperators() returns a super set of
> ascendant operators, which causes wrong DPP source removal.
> Please check out the attached slides for detailed explanation.
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