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From "ramkrishna.s.vasudevan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-14841) Allow Dictionary to work with BytebufferedCells
Date Mon, 04 Jan 2016 08:18:39 GMT

    [ https://issues.apache.org/jira/browse/HBASE-14841?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15080813#comment-15080813

ramkrishna.s.vasudevan commented on HBASE-14841:

Better to leave this JIRA for now. In case of TagCompressionContext - We do compressTags and
in that we try to find if the tag is in dictionary and if not found we add it.
Now before adding we try to do a copy so that we remove the reference to the bigger byte[]
backing the Cells.
If the tag is not found in the dictionary we any way add it to the output stream as it is
and for that we need the byte[]. (because it is a ByteArrayOutputStream).

If we try to work with BB here - In case of adding to the Dictionary we need to do a copy
to a local byte[] anyway inorder to create a dictionary. 
Now for finding the entry in the dictionary we need to modify the Node and its type to work
with ByteBuffers but if we add it as a byte[] there is no point in trying to find it with
BB and so we need to do a copy there. 

With the existing code if a Cell is offheap we are doing a onheap copy to a byte[] every time
- and this is causing one more copy when we see that the entry is not there in the dictionary.
I think overall doing changes to avoid such copies not sure how much benefits it is going
to yield us. So better to defer this JIRA for future and implement it when it makes sense
to us. 
Anyway will attach a patch with minimal changes that will allow the cells to work with Offheap

> Allow Dictionary to work with BytebufferedCells
> -----------------------------------------------
>                 Key: HBASE-14841
>                 URL: https://issues.apache.org/jira/browse/HBASE-14841
>             Project: HBase
>          Issue Type: Sub-task
>          Components: regionserver, Scanners
>            Reporter: ramkrishna.s.vasudevan
>            Assignee: ramkrishna.s.vasudevan
> This is part of HBASE-14832 where we need to ensure that while BBCells are getting compacted
the TagCompression part should be working with BBCells.

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