[jira] [Commented] (CASSANDRA-5515) Track sstable coldness

["Tyler Hobbs (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-5515?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13726753#comment-13726753 ] 

Tyler Hobbs commented on CASSANDRA-5515:
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bq. Maybe get fancy and do a reservoir-sampling histogram? Metrics makes that easy.

I could see that being useful during steady state, but there doesn't appear to be an easy way to serialize and rebuild those, which either means we would need a somewhat custom implementation, or we wouldn't have reliable information on startup.  (The custom implementation could support dump and restore, or perhaps just expose a notion of "confidence".)

Perhaps we should spend some time looking at the use cases before investing too much effort in this?
                
> Track sstable coldness
> ----------------------
>
>                 Key: CASSANDRA-5515
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-5515
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Core
>            Reporter: Jonathan Ellis
>            Assignee: Tyler Hobbs
>             Fix For: 2.0.1
>
>         Attachments: 0001-Track-row-read-counts-in-SSTR.patch
>
>
> Keeping a count of reads per-sstable would allow STCS to automatically ignore cold data rather than recompacting it constantly with hot data, dramatically reducing compaction load for typical time series applications and others with time-correlated access patterns.  We would not need a separate age-tiered compaction strategy.
> (This will really be useful in conjunction with CASSANDRA-5514.)

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