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https://issues.apache.org/jira/browse/HIVE-11652?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15767233#comment-15767233
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Jesus Camacho Rodriguez commented on HIVE-11652:
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[~dhiraj.kumar], thanks for creating the issue.
I meant keeping position per node, not only a single position for last node.
That is why it would add memory pressure.
{quote}
In fact that finding position itself is not a problem, but
ASTNode.getChildren() invocation is problem.
{quote}
Yes, that was my guess when I checked the code and probably we should focus on
this part.
Each time we call that method, a new list is created and its children are
copied to it; I do not not know the original reason why we overwrote
_getChildren_ to do that in every call and if there is actually a good reason
for that. I would expect that by default, we return the original list; in turn,
we return a copy if it is explicitly pointed out (via boolean).
In any case, we can continue the discussion in HIVE-15486.
> 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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