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https://issues.apache.org/jira/browse/PHOENIX-2405?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15338744#comment-15338744
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ASF GitHub Bot commented on PHOENIX-2405:
-----------------------------------------
GitHub user RCheungIT opened a pull request:
https://github.com/apache/phoenix/pull/175
PHOENIX-2405 Not for merge, just request a review to check whether I'm on
the right way
https://issues.apache.org/jira/browse/PHOENIX-2405
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/RCheungIT/phoenix PHOENIX-2405-HBase-1.2
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/phoenix/pull/175.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #175
----
commit 6566ccd5fa4e8fbfa4fea4e743ca56143d17bc48
Author: RCheungIT <hubert.zh...@outlook.com>
Date: 2016-05-27T17:12:41Z
PHOENIX-2405 Improve performance and stability of server side sort for
ORDER BY
----
> Improve performance and stability of server side sort for ORDER BY
> ------------------------------------------------------------------
>
> Key: PHOENIX-2405
> URL: https://issues.apache.org/jira/browse/PHOENIX-2405
> Project: Phoenix
> Issue Type: Bug
> Reporter: James Taylor
> Assignee: Haoran Zhang
> Labels: gsoc2016
> Fix For: 4.8.0
>
>
> We currently use memory mapped files to buffer data as it's being sorted in
> an ORDER BY (see MappedByteBufferQueue). The following types of exceptions
> have been seen to occur:
> {code}
> Caused by: java.lang.OutOfMemoryError: Map failed
> at sun.nio.ch.FileChannelImpl.map0(Native Method)
> at sun.nio.ch.FileChannelImpl.map(FileChannelImpl.java:904)
> {code}
> [~apurtell] has read that memory mapped files are not cleaned up after very
> well in Java:
> {quote}
> "Map failed" means the JVM ran out of virtual address space. If you search
> around stack overflow for suggestions on what to do when your app (in this
> case Phoenix) encounters this issue when using mapped buffers, the answers
> tend toward manually cleaning up the mapped buffers or explicitly triggering
> a full GC. See
> http://stackoverflow.com/questions/8553158/prevent-outofmemory-when-using-java-nio-mappedbytebuffer
> for example. There are apparently long standing JVM/JRE problems with
> reclamation of mapped buffers. I think we may want to explore in Phoenix a
> different way to achieve what the current code is doing.
> {quote}
> Instead of using memory mapped files, we could use heap memory, or perhaps
> there are other mechanisms too.
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