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https://issues.apache.org/jira/browse/HIVE-29534?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Stamatis Zampetakis updated HIVE-29534:
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Summary: Missing NDV and HLL stats for DATE/TIMESTAMP columns during
optimization (was: Statistics: StatsUtils::getColStatistics does not set
NDV/some other fields for DATE/TIMESTAMP columns)
> Missing NDV and HLL stats for DATE/TIMESTAMP columns during optimization
> ------------------------------------------------------------------------
>
> Key: HIVE-29534
> URL: https://issues.apache.org/jira/browse/HIVE-29534
> Project: Hive
> Issue Type: Bug
> Reporter: Konstantin Bereznyakov
> Assignee: Konstantin Bereznyakov
> Priority: Major
> Labels: pull-request-available
> Attachments: 6406.patch
>
>
> Technically, the method is missing stats for multiple data types. The most
> important ones seem to be: setCountDistint() for DATE_TYPE_NAME and
> TIMESTAMP_TYPE_NAME
> The TIMESTAMP datatype could also benefit from setBitVectors(), for which the
> info also appears to be available.
> As the result of this, the NDV of columns of this data type is assigned a
> value of 0. which could negatively impact execution planning of some queries
> [https://github.com/apache/hive/blob/bbd83dff5bfc8b8ce018476391469da3331216dd/ql/src/java/org/apache/hadoop/hive/ql/stats/StatsUtils.java#L840]
> [https://github.com/apache/hive/blob/bbd83dff5bfc8b8ce018476391469da3331216dd/ql/src/java/org/apache/hadoop/hive/ql/stats/StatsUtils.java#L870]
> Adding this info seems to change the output of about 100 .out files
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