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From "Matt Corgan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-9440) Pass blocks of KVs from HFile scanner to the StoreFileScanner and up
Date Fri, 06 Sep 2013 20:47:52 GMT

    [ https://issues.apache.org/jira/browse/HBASE-9440?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13760600#comment-13760600
] 

Matt Corgan commented on HBASE-9440:
------------------------------------

It's a somewhat advanced optimization, but I've always hoped to see block level transfer of
data like this.  Both for compactions and long scans.  For compactions it's probably quite
often that all the cells in a block will remain contiguous, in which case you could save the
decompression, decoding, heap logic, encoding, compression steps.  Just hand the byte[] through
to the new file.  For the client case, maybe make it a setting to bring whole blocks back
to the client (as soon as any part of a block is needed) and do filtering logic client-side.
                
> Pass blocks of KVs from HFile scanner to the StoreFileScanner and up
> --------------------------------------------------------------------
>
>                 Key: HBASE-9440
>                 URL: https://issues.apache.org/jira/browse/HBASE-9440
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Lars Hofhansl
>
> Currently we read KVs from an HFileScanner one-by-one and pass them up the scanner/heap
tree. Many time the ranges of KVs retrieved from StoreFileScanner (by StoreScanners) and HFileScanner
(by StoreFileScanner) will be non-overlapping. If chunks of KVs do not overlap we can sort
entire chunks just by comparing the start/end key of the chunk. Only if chunks are overlapping
do we need to sort KV by KV as we do now.
> I have no patch, but I wanted to float this idea. 

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