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https://issues.apache.org/jira/browse/SPARK-30565?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17057224#comment-17057224
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Peter Toth commented on SPARK-30565:
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I looked into this and the performance drop is due to the 1.2.1 -> 2.3.6 Hive
version change we introduced in Spark 3. I measured that
{{org.apache.hadoop.hive.ql.io.orc.ReaderImpl}} in {{hive-exec-2.3.6-core.jar}}
is ~3-5 times slower than in {{hive-exec-1.2.1.spark2.jar}}.
> Regression in the ORC benchmark
> -------------------------------
>
> Key: SPARK-30565
> URL: https://issues.apache.org/jira/browse/SPARK-30565
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 3.0.0
> Reporter: Maxim Gekk
> Priority: Major
>
> New benchmark results generated in the PR
> [https://github.com/apache/spark/pull/27078] show regression ~3 times.
> Before:
> {code}
> Hive built-in ORC 520 531
> 8 2.0 495.8 0.6X
> {code}
> https://github.com/apache/spark/pull/27078/files#diff-42fe5f1ef10d8f9f274fc89b2c8d140dL138
> After:
> {code}
> Hive built-in ORC 1761 1792
> 43 0.6 1679.3 0.1X
> {code}
> https://github.com/apache/spark/pull/27078/files#diff-42fe5f1ef10d8f9f274fc89b2c8d140dR138
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