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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PHOENIX-5123) Avoid using MappedByteBuffers for server side GROUP BY
Date Tue, 05 Feb 2019 05:31:00 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-5123?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16760473#comment-16760473
] 

Lars Hofhansl commented on PHOENIX-5123:
----------------------------------------

Looked at it some. Doesn't look that hard. Not sure I'll have time in the next few days. If
someone wants to pick this up... Basically when we read we need to read a byte from a file
(rather than a mapped byte buffer)

And looking more... We're only MappedByteBuffer to bring in byte[] from a file and to write
a byte[] to a file. Seems very wasteful to go through a MappedByteBuffer just for that. If
we had at least used the buffer directly... But, no we don't :)

> Avoid using MappedByteBuffers for server side GROUP BY
> ------------------------------------------------------
>
>                 Key: PHOENIX-5123
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-5123
>             Project: Phoenix
>          Issue Type: Bug
>            Reporter: Lars Hofhansl
>            Priority: Major
>
> Like PHOENIX-5120 but for GROUP BY.
> Solution is a bit more tricky, since outline for sorting the access here is truly random.
> [~apurtell] suggests to perhaps just use a RandomAccessFile for this.
> (I'm not sure that uses under the hood, though)



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