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From "ramkrishna.s.vasudevan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-10974) Improve DBEs read performance by avoiding byte array deep copies for key[] and value[]
Date Wed, 16 Apr 2014 05:40:15 GMT

    [ https://issues.apache.org/jira/browse/HBASE-10974?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13970454#comment-13970454
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ramkrishna.s.vasudevan commented on HBASE-10974:
------------------------------------------------

Retrieving a single KV
======================
If i need the last Kv in a block and in all of them there are 50 common bytes then (assume
1000 keys)
(50 * 1000 = 50000) + 50 = 50050

But with the latest code
(100 * 1000 = 10000) will happen

Scans
=====
But in case of scans, if i need to retrieve the 1000 keys from the block
(50 * 1000 = 50000) + (100 * 1000 = 100000) = 150000. Because a deep copy will also happen
With latest code
(100 * 1000 = 10000)

> Improve DBEs read performance by avoiding byte array deep copies for key[] and value[]
> --------------------------------------------------------------------------------------
>
>                 Key: HBASE-10974
>                 URL: https://issues.apache.org/jira/browse/HBASE-10974
>             Project: HBase
>          Issue Type: Improvement
>          Components: Scanners
>    Affects Versions: 0.99.0
>            Reporter: ramkrishna.s.vasudevan
>            Assignee: ramkrishna.s.vasudevan
>             Fix For: 0.99.0
>
>         Attachments: HBASE-10974_1.patch
>
>
> As part of HBASE-10801, we  tried to reduce the copy of the value [] in forming the KV
from the DBEs. 
> The keys required copying and this was restricting us in using Cells and always wanted
to copy to be done.
> The idea here is to replace the key byte[] as ByteBuffer and create a consecutive stream
of the keys (currently the same byte[] is used and hence the copy).  Use offset and length
to track this key bytebuffer.
> The copy of the encoded format to normal Key format is definitely needed and can't be
avoided but we could always avoid the deep copy of the bytes to form a KV and thus use cells
effectively. Working on a patch, will post it soon.



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