[jira] [Commented] (HBASE-14841) Allow Dictionary to work with BytebufferedCells

["ramkrishna.s.vasudevan (JIRA)" <ji...@apache.org>]

    [ 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 BBs.




> 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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