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https://issues.apache.org/jira/browse/HBASE-24859?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17223863#comment-17223863
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Andrew Kyle Purtell commented on HBASE-24859:
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Why is this not being committed to more than branch-1?
I think it's a violation of our policy to commit from master first down to
releasing branches because the change seems to apply to those later branches as
well. I found the changes apply with only minor fixup needed to branch-2
(branch-2.3, specifically)
> Optimize in-memory representation of mapreduce TableSplit objects
> -----------------------------------------------------------------
>
> Key: HBASE-24859
> URL: https://issues.apache.org/jira/browse/HBASE-24859
> Project: HBase
> Issue Type: Improvement
> Components: mapreduce
> Affects Versions: 3.0.0-alpha-1, 2.3.3, 1.7.0, 2.4.0, 2.2.7
> Reporter: Sandeep Pal
> Assignee: Sandeep Pal
> Priority: Major
> Fix For: 1.7.0
>
> Attachments: Screen Shot 2020-08-26 at 8.44.34 AM.png, hbase-24859.png
>
>
> It has been observed that when the table has too many regions, MR jobs
> consume a lot of memory in the client. This is because we keep the region
> level information in memory and the memory heavy object is TableSplit because
> of the Scan object as a part of it.
> However, it looks like the TableInputFormat for single table doesn't need to
> store the scan object in the TableSplit because we do not use it and all the
> splits are expected to have the exact same scan object. In TableInputFormat
> we use the scan object directly from the MR conf.
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