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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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