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https://issues.apache.org/jira/browse/HIVE-11652?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15766640#comment-15766640
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Jesus Camacho Rodriguez commented on HIVE-11652:
------------------------------------------------

PS. I have just checked the _getChildren_ method in _ASTNode_: it creates a 
copy of the list of the original children of the AST node. It might be possible 
to return the list itself for the walker, thus preventing the copy of the list, 
which is expensive.

Cc [~dhiraj.kumar]

> Avoid expensive call to removeAll in DefaultGraphWalker
> -------------------------------------------------------
>
>                 Key: HIVE-11652
>                 URL: https://issues.apache.org/jira/browse/HIVE-11652
>             Project: Hive
>          Issue Type: Bug
>          Components: Logical Optimizer, Physical Optimizer
>    Affects Versions: 1.3.0, 2.0.0
>            Reporter: Jesus Camacho Rodriguez
>            Assignee: Jesus Camacho Rodriguez
>             Fix For: 1.3.0, 2.0.0
>
>         Attachments: HIVE-11652.01.patch, HIVE-11652.02.patch, 
> HIVE-11652.patch
>
>
> When the plan is too large, the removeAll call in DefaultGraphWalker (line 
> 140) will take very long as it will have to go through the list looking for 
> each of the nodes. We try to get rid of this call by rewriting the logic in 
> the walker.



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