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From "Jean-Daniel Cryans (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-11120) Update documentation about major compaction algorithm
Date Thu, 22 May 2014 21:14:02 GMT

    [ https://issues.apache.org/jira/browse/HBASE-11120?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14006480#comment-14006480
] 

Jean-Daniel Cryans commented on HBASE-11120:
--------------------------------------------

On top of Sergey's comments:

This could also use a sentence regarding TTLs, they are simply filtered out and tombstones
aren't created:

{noformat}
bq. <title>Compaction and Deletions</title>
{noformat}

Same kind of comment for this para, the old versions are filtered more than deleted:

{noformat}
+            <title>Compaction and Versions</title>
{noformat}

One thing bothers me about this para:

{noformat}
+            <para>The compaction algorithms used by HBase have evolved over time. HBase
0.96
+              introduced a new algorithm for compaction file selection. To find out about
the old
+              algorithm, see <xref
+                linkend="compaction" />. The rest of this section describes the new algorithm,
which
+              was implemented in <link
+                xlink:href="https://issues.apache.org/jira/browse/HBASE-7842">HBASE-7842</link>.
{noformat}

What's written next is much more about how to pick the files that will then be considered
for compaction than the actual new policy which is in ExploringCompactionPolicy.java. In other
words, the text that follows what I just quoted is ok but not really new in 0.96 via HBASE-7842,
and it seems to me that we should explain what HBASE-7842 does.

> Update documentation about major compaction algorithm
> -----------------------------------------------------
>
>                 Key: HBASE-11120
>                 URL: https://issues.apache.org/jira/browse/HBASE-11120
>             Project: HBase
>          Issue Type: Bug
>          Components: Compaction, documentation
>    Affects Versions: 0.98.2
>            Reporter: Misty Stanley-Jones
>            Assignee: Misty Stanley-Jones
>         Attachments: HBASE-11120.patch
>
>
> [14:20:38]  <jdcryans>	 seems that there's http://hbase.apache.org/book.html#compaction
and http://hbase.apache.org/book.html#managed.compactions
> [14:20:56]  <jdcryans>	 the latter doesn't say much, except that you should manage
them
> [14:21:44]  <jdcryans>	 the former gives a good description of the _old_ selection
algo
> [14:45:25]  <jdcryans>	 this is the new selection algo since C5 / 0.96.0: https://issues.apache.org/jira/browse/HBASE-7842



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