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https://issues.apache.org/jira/browse/HBASE-10974?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14172499#comment-14172499
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Anoop Sam John commented on HBASE-10974:
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{code}
currentBuffer = buffer;
+ // Allocate every time we get a new block
+ // Would be great if from the block we know how much is key part and how
+ // much is for value part(the unencoded one). If this value exceeds we
+ // may need to do a copy
+ // TODO : Get the unencoded key length from the hfileblock
+ current.keyBuffer = ByteBuffer.allocate(currentBuffer.capacity() * 16);
{code}
We allocate a very big size buffer for the key? 'currentBuffer' is the buffer
containing the whole block data and we allocate 16 times bigger buffer! Not
getting why you want this Ram.
> 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: 0.99.2
>
> 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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