[jira] [Commented] (SPARK-32995) CostBasedJoinReorder optimizer rule should be idempotent

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

    [ https://issues.apache.org/jira/browse/SPARK-32995?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17202300#comment-17202300 ] 

Apache Spark commented on SPARK-32995:
--------------------------------------

User 'tanelk' has created a pull request for this issue:
https://github.com/apache/spark/pull/29871

> CostBasedJoinReorder optimizer rule should be idempotent
> --------------------------------------------------------
>
>                 Key: SPARK-32995
>                 URL: https://issues.apache.org/jira/browse/SPARK-32995
>             Project: Spark
>          Issue Type: Improvement
>          Components: SQL
>    Affects Versions: 3.1.0
>            Reporter: Tanel Kiis
>            Priority: Minor
>
> The CostBasedJoinReorder has currently the following comment:
> {code}
>     // Since join costs in AQP can change between multiple runs, there is no reason that we have an
>     // idempotence enforcement on this batch. We thus make it FixedPoint(1) instead of Once.
> {code} 
> This is incorrect reasoning.
> In the optimizer, we mean that a batch is idempotent, when applying it for the second time in a row (without changing anything) it does not change the plan at all. 



--
This message was sent by Atlassian Jira
(v8.3.4#803005)

---------------------------------------------------------------------
To unsubscribe, e-mail: issues-unsubscribe@spark.apache.org
For additional commands, e-mail: issues-help@spark.apache.org