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Posted to issues@spark.apache.org by "jiaan.geng (Jira)" <ji...@apache.org> on 2021/05/08 09:17:00 UTC
[jira] [Commented] (SPARK-34257) Improve performance for last_value
over unbounded window frame
[ https://issues.apache.org/jira/browse/SPARK-34257?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17341252#comment-17341252 ]
jiaan.geng commented on SPARK-34257:
------------------------------------
Because it's not worth do the optimization for last_value only.
We suspend this work.
> Improve performance for last_value over unbounded window frame
> --------------------------------------------------------------
>
> Key: SPARK-34257
> URL: https://issues.apache.org/jira/browse/SPARK-34257
> Project: Spark
> Issue Type: Sub-task
> Components: SQL
> Affects Versions: 3.2.0
> Reporter: jiaan.geng
> Priority: Major
>
> The current implement of `last_value` over unbounded window frame will execute `updateExpressions` multiple times.
> In fact, `last_value` only execute `updateExpressions` once on the last row.
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