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https://issues.apache.org/jira/browse/HIVE-10261?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14485439#comment-14485439
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Mostafa Mokhtar commented on HIVE-10261:
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[~lirui]
Can you please attach an explain plan along with query and actual number of
rows for the operator with underestimation?
> Data size can be underestimated when computed with partial column stats
> -----------------------------------------------------------------------
>
> Key: HIVE-10261
> URL: https://issues.apache.org/jira/browse/HIVE-10261
> Project: Hive
> Issue Type: Bug
> Reporter: Rui Li
>
> With {{hive.stats.fetch.column.stats=true}}, we'll estimate data size with
> column stats when annotating operators with statistics. However, when column
> stats is partial, we're likely to underestimate data size, which may hurt
> performance, e.g. picking an inappropriate small table for map join.
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