[jira] [Commented] (SPARK-21083) Consider staleness when collecting column stats

["Apache Spark (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-21083?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16048139#comment-16048139 ] 

Apache Spark commented on SPARK-21083:
--------------------------------------

User 'wzhfy' has created a pull request for this issue:
https://github.com/apache/spark/pull/18292

> Consider staleness when collecting column stats
> -----------------------------------------------
>
>                 Key: SPARK-21083
>                 URL: https://issues.apache.org/jira/browse/SPARK-21083
>             Project: Spark
>          Issue Type: Sub-task
>          Components: SQL
>    Affects Versions: 2.3.0
>            Reporter: Zhenhua Wang
>
> Suppose we already collected column stats for some columns before, then, when we collect column stats for other columns:
> * If the table is changed during two collecting actions, we need to remove these stale column stats, only keep the latest stats.
> * Otherwise, combine these two sets of column stats.
> Note that we always update sizeInBytes/rowCount when collecting column stats, that logic doesn't need change.



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