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https://issues.apache.org/jira/browse/HIVE-30070?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18116737#comment-18116737
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Stamatis Zampetakis commented on HIVE-30070:
--------------------------------------------
The complete flamegraph can be found in [^profile.html]
> Conversion to Map join is very slow for Iceberg tables on S3
> ------------------------------------------------------------
>
> Key: HIVE-30070
> URL: https://issues.apache.org/jira/browse/HIVE-30070
> Project: Hive
> Issue Type: Bug
> Components: HiveServer2
> Reporter: Stamatis Zampetakis
> Assignee: Stamatis Zampetakis
> Priority: Major
> Attachments: convert-join-map-join.png, profile.html
>
>
> The Conversion of a common shuffle join to map join (ConvertJoinMapJoin) is
> very slow when we are dealing with Iceberg tables on S3.
> !convert-join-map-join.png!
> The flamegraph was obtained via async profiler while running
> TestTPCDSIcebergCliDriver (HIVE-30034) with hive.auto.convert.sortmerge.join
> enabled.
> {noformat}
> mvn test -Dtest=TestTPCDSIcebergCliDriver -Dtest.output.overwrite
> -Dqfile_regex=cbo_query4.*
> {noformat}
>
> A large amount of time is spent on
> {{AvgPartitionSizeBasedBigTableSelectorForAutoSMJ.getBigTablePosition}} and
> in particular inside the {{S3AFileSystem.getContentSummary}} operation.
> Since this slowness came up in a test setup it has to be verified to what
> extend it affects production deployments.
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