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https://issues.apache.org/jira/browse/HBASE-20045?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16379420#comment-16379420
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Jean-Marc Spaggiari commented on HBASE-20045:
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Ok. Just ran a small test.
PE sequentialWrites 10000 rows. Flush ->`1500 bloks in offheap
PE sequentialWrites 10000 rows. Flush ->` +1500 bloks in offheap
PE sequentialWrites 10000 rows. Flush ->`+1500 bloks in offheap
At that point I have about 4700 blocks in offheap.
major_compact TestTable -> 0 blocks in memory. So on compactions, block are not
loaded back into memory. Which reduces a lot the benefit for caching on
writes/flushs.
> When running compaction, cache recent blocks.
> ---------------------------------------------
>
> Key: HBASE-20045
> URL: https://issues.apache.org/jira/browse/HBASE-20045
> Project: HBase
> Issue Type: New Feature
> Components: BlockCache, Compaction
> Affects Versions: 2.0.0-beta-1
> Reporter: Jean-Marc Spaggiari
> Priority: Major
>
> HBase already allows to cache blocks on flush. This is very useful for
> usecases where most queries are against recent data. However, as soon as
> their is a compaction, those blocks are evicted. It will be interesting to
> have a table level parameter to say "When compacting, cache blocks less than
> 24 hours old". That way, when running compaction, all blocks where some data
> are less than 24h hold, will be automatically cached.
>
> Very useful for table design where there is TS in the key but a long history
> (Like a year of sensor data).
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