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From "Tyler Hobbs (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-11035) Use cardinality estimation to pick better compaction candidates for STCS (SizeTieredCompactionStrategy)
Date Fri, 19 Feb 2016 18:15:18 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-11035?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15154579#comment-15154579
] 

Tyler Hobbs commented on CASSANDRA-11035:
-----------------------------------------

In combination with a minimum threshold, we could also potentially increase the sstable size
variation within a bucket.  In other words, instead of requiring sstables in a bucket to be
within 50% of the average size, allow them to be within 75% of the average size.  If we know
that sstables have a lot of overlap, it makes sense to be a little more flexible about the
sizes.

However, if we do implement a minimum threshold, we should probably add a cap on the max number
of sstables (for STCS, at least).  Otherwise, you might see unbounded sstable growth for something
like a Users table.

> Use cardinality estimation to pick better compaction candidates for STCS (SizeTieredCompactionStrategy)
> -------------------------------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-11035
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-11035
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Compaction
>            Reporter: Wei Deng
>            Assignee: Marcus Eriksson
>
> This was initially mentioned in this blog post http://www.datastax.com/dev/blog/improving-compaction-in-cassandra-with-cardinality-estimation
but I couldn't find any existing JIRA for it. As stated by [~jbellis], "Potentially even more
useful would be using cardinality estimation to pick better compaction candidates. Instead
of blindly merging sstables of a similar size a la SizeTieredCompactionStrategy." The L0 STCS
in LCS should benefit as well.



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