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https://issues.apache.org/jira/browse/HBASE-7519?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13547558#comment-13547558
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Sergey Shelukhin commented on HBASE-7519:
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>From the discussion today; from my understanding leveldb key ranges in
>different files may overlap between levels; that means that compaction for a
>range must do something with the leftover bits of the files, or keep old files
>for other ranges.
E.g. if I have two levels somewhere (in no particular order) - lN with [1,5),
[6, 10] files and lM with [1, 4), [4, 7), [8, 10] files, compaction for [4, 7]
must include both of the lN files, and produce some parts of them, or keep
them, for the reads from other ranges. If instead it uses the largest
overlapping range to avoid only using parts of the files, all ranges would
eventually merge.
That would mean Compactor and other things also needs to change significantly
(and become pluggable?) afaisee.
> Support level compaction
> ------------------------
>
> Key: HBASE-7519
> URL: https://issues.apache.org/jira/browse/HBASE-7519
> Project: HBase
> Issue Type: New Feature
> Components: Compaction
> Reporter: Jimmy Xiang
> Assignee: Jimmy Xiang
> Attachments: level-compaction.pdf
>
>
> The level compaction algorithm may help HBase for some use cases, for
> example, read heavy loads (especially, just one version is used), relative
> small key space updated frequently.
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