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https://issues.apache.org/jira/browse/HBASE-25972?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17847388#comment-17847388
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Andrew Kyle Purtell commented on HBASE-25972:
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Thanks [~bbeaudreault]. I'm only waiting on another precommit to confirm a
spotless fix and then will merge this back all the way through 2.6 into 2.5.
> Dual File Compaction
> --------------------
>
> Key: HBASE-25972
> URL: https://issues.apache.org/jira/browse/HBASE-25972
> Project: HBase
> Issue Type: Improvement
> Reporter: Kadir Ozdemir
> Assignee: Kadir Ozdemir
> Priority: Major
> Labels: pull-request-available
> Fix For: 2.7.0, 3.0.0-beta-2
>
>
> HBase stores tables row by row in its files, HFiles. An HFile is composed of
> blocks. The number of rows stored in a block depends on the row sizes. The
> number of rows per block gets lower when rows get larger on disk due to
> multiple row versions since HBase stores all row versions sequentially in the
> same HFile after compaction. However, applications (e.g., Phoenix) mostly
> query the most recent row versions.
> The default compactor in HBase compacts HFiles into one file. This Jira
> introduces a new store file writer which writes the retained cells by
> compaction into two files, which will be called DualFileWriter. One of these
> files will include the live cells. This file will be called a live-version
> file. The other file will include the rest of the cells, that is, historical
> versions. This file will be called a historical-version file. DualFileWriter
> will work with the default compactor.
> The historical files will not be read for the scans scanning latest row
> versions. This eliminates scanning unnecessary cell versions in compacted
> files and thus it is expected to improve performance of these scans.
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