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From "He Yongqiang (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5313) Restructure hfiles layout for better compression
Date Wed, 08 Feb 2012 20:18:59 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5313?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13203935#comment-13203935
] 

He Yongqiang commented on HBASE-5313:
-------------------------------------

"I suppose we could use the value length from the key, then know we have nth key and by using
the value length of all 1 to n-1 keys to find the value."
Yes. The value length is stored in the key header. The key header is cheap. And can always
be decompressed without a big cpu cost.
                
> Restructure hfiles layout for better compression
> ------------------------------------------------
>
>                 Key: HBASE-5313
>                 URL: https://issues.apache.org/jira/browse/HBASE-5313
>             Project: HBase
>          Issue Type: Improvement
>          Components: io
>            Reporter: dhruba borthakur
>            Assignee: dhruba borthakur
>
> A HFile block contain a stream of key-values. Can we can organize these kvs on the disk
in a better way so that we get much greater compression ratios?
> One option (thanks Prakash) is to store all the keys in the beginning of the block (let's
call this the key-section) and then store all their corresponding values towards the end of
the block. This will allow us to not-even decompress the values when we are scanning and skipping
over rows in the block.
> Any other ideas? 

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