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https://issues.apache.org/jira/browse/SPARK-23304?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16353325#comment-16353325
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Wenchen Fan commented on SPARK-23304:
-------------------------------------
I didn't follow the discussion here closely, but FYI, the document of
`Dataset.coalesce` says:
{code:java}
* Returns a new Dataset that has exactly `numPartitions` partitions, when the
fewer partitions
* are requested. If a larger number of partitions is requested, it will stay at
the current
* number of partitions{code}
> Spark SQL coalesce() against hive not working
> ---------------------------------------------
>
> Key: SPARK-23304
> URL: https://issues.apache.org/jira/browse/SPARK-23304
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 2.2.1, 2.3.0
> Reporter: Thomas Graves
> Assignee: Xiao Li
> Priority: Major
> Attachments: spark22_oldorc_explain.txt, spark23_oldorc_explain.txt,
> spark23_oldorc_explain_convermetastoreorcfalse.txt
>
>
> The query below seems to ignore the coalesce. This is running spark 2.2 or
> spark 2.3 against hive, which is reading orc:
>
> Query:
> spark.sql("SELECT COUNT(DISTINCT(something)) FROM sometable WHERE dt >=
> '20170301' AND dt <= '20170331' AND something IS NOT
> NULL").coalesce(160000).show()
>
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