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Date: Fri, 9 Mar 2012 21:54:59 +0000 (UTC)
From: "Zhihong Yu (Commented) (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (HBASE-4608) HLog Compression
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    [ https://issues.apache.org/jira/browse/HBASE-4608?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13226519#comment-13226519 ] 

Zhihong Yu commented on HBASE-4608:
-----------------------------------

{code}
+  public static int hashBytes(byte[] bytes, int offset, int length) {
{code}
The above method allows to start computation at specified offset while existing hashCode() doesn't have this parameter.

The remark of putting compression flag as sequence file attribute is really good.
Looking at SequenceFile.Sorter.cloneFileAttributes(), I don't see a convenient way for doing above.

For HLogKey, can we designate version of -2 for representing compressed HLogKey ? If HLogKey isn't compressed, we write -1.
                
> HLog Compression
> ----------------
>
>                 Key: HBASE-4608
>                 URL: https://issues.apache.org/jira/browse/HBASE-4608
>             Project: HBase
>          Issue Type: New Feature
>            Reporter: Li Pi
>            Assignee: Li Pi
>             Fix For: 0.94.0
>
>         Attachments: 4608-v19.txt, 4608v1.txt, 4608v13.txt, 4608v13.txt, 4608v14.txt, 4608v15.txt, 4608v16.txt, 4608v17.txt, 4608v18.txt, 4608v5.txt, 4608v6.txt, 4608v7.txt, 4608v8fixed.txt
>
>
> The current bottleneck to HBase write speed is replicating the WAL appends across different datanodes. We can speed up this process by compressing the HLog. Current plan involves using a dictionary to compress table name, region id, cf name, and possibly other bits of repeated data. Also, HLog format may be changed in other ways to produce a smaller HLog.

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