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From "huaxiang sun (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-17172) Optimize major mob compaction with _del files
Date Thu, 24 Nov 2016 08:03:58 GMT

    [ https://issues.apache.org/jira/browse/HBASE-17172?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15692581#comment-15692581
] 

huaxiang sun commented on HBASE-17172:
--------------------------------------

Thanks [~jingcheng.du@intel.com]! Distributed compaction is definitely helpful even with the
minor compaction, consider that mob compaction needs to acquire a table lock. The purpose
of major compaction is trying to reduce the number of files. With HBASE-16891, users may still
choose to disable mob compaction chore and run mob compaction manually at scheduled maintenance.
To keep delete marker in hbase files in mob-enabled cf is one way to avoid .del files, the
concern is that it is inconsistent with non-mob cfs (maybe this can be provided as option
through config?). Another way may be to optimize it as the current jira suggests. For an example,
user deletes some rows for one or two regions, after compaction, there will be .del files
created. With the current major mob compaction, these .del files will be included in compacting
of files for other regions which is not necessary, the net effect is that all mob files will
be re-compacted. More ideas about how to optimize it are welcome, but I think distributed
mob compaction is definitely needed, thanks.

> Optimize major mob compaction with _del files
> ---------------------------------------------
>
>                 Key: HBASE-17172
>                 URL: https://issues.apache.org/jira/browse/HBASE-17172
>             Project: HBase
>          Issue Type: Improvement
>          Components: mob
>    Affects Versions: 2.0.0
>            Reporter: huaxiang sun
>            Assignee: huaxiang sun
>
> Today, when there is a _del file in mobdir, with major mob compaction, every mob file
will be recompacted, this causes lots of IO and slow down major mob compaction (may take months
to finish). This needs to be improved. A few ideas are: 
> 1) Do not compact all _del files into one, instead, compact them based on groups with
startKey as the key. Then use firstKey/startKey to make each mob file to see if the _del file
needs to be included for this partition.
> 2). Based on the timerange of the _del file, compaction for files after that timerange
does not need to include the _del file as these are newer files.



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