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Branimir Lambov commented on CASSANDRA-16782:
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I have some general questions about the improvement. It looks like it is a
combination of two things:
* A drastic increase of STCS's limit for max sstables in a compaction, and
* A preference of the STCS level to compact based on the number of sstables,
which only apply to uses of STCS in LCS and TWCS.
I can see a lot of value in the latter, but why not apply it always, including
plain STCS? STCS's selection of bucket to compact does result in accumulation
of sstables on the smallest-sstables bucket and at DataStax we were recently
discussing selecting the most populous bucket as a possible solution to this
problem, which might be good enough even without raising the max limit. I
personally could not find any downsides to it, and I wonder why you would
prefer to restrict its usage?
The former we can achieve by configuration, can't we? (Perhaps also adding a
max size limit.) Speaking of which, is there a reason to place the new settings
in {{cassandra.yaml}} instead of compaction parameters?
> Improve the way we pick sstables for STCS-in-L0 and in TWCS 'current' window
> ----------------------------------------------------------------------------
>
> Key: CASSANDRA-16782
> URL: https://issues.apache.org/jira/browse/CASSANDRA-16782
> Project: Cassandra
> Issue Type: Improvement
> Components: Local/Compaction/LCS, Local/Compaction/TWCS
> Reporter: Marcus Eriksson
> Assignee: Marcus Eriksson
> Priority: Normal
> Fix For: 4.x
>
>
> The goal when being behind in L0 should always be to get the number of
> sstables down to a reasonable level as soon as possible. Currently it is
> common that we run compactions on the large sstables but leave thousands of
> tiny sstables behind.
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