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From "Carl Yeksigian (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-10979) LCS doesn't do L0 STC on new tables while an L0->L1 compaction is in progress
Date Wed, 13 Jan 2016 16:29:39 GMT


Carl Yeksigian commented on CASSANDRA-10979:

I'm fine with this going in 2.2 as it's not an intrusive fix, but I also think this is more
of an improvement than a bug fix.

While this will reduce the number of sstables on a read when L0 is backed up, the problem
remains that L0 cannot keep up with the amount of incoming data. Once we finish the L0->L1
compaction, we will be running the L0 STCS since we will have a level that is oversized which
will also cause us to check L0 again.

> LCS doesn't do L0 STC on new tables while an L0->L1 compaction is in progress
> -----------------------------------------------------------------------------
>                 Key: CASSANDRA-10979
>                 URL:
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Compaction
>         Environment: 2.1.11 / 4.8.3 DSE.
>            Reporter: Jeff Ferland
>            Assignee: Carl Yeksigian
>              Labels: compaction, leveled
>             Fix For: 3.x
>         Attachments: 10979-2.1.txt
> Reading code from
and comparing with behavior shown in,
the following happens:
> Score for L1,L2,and L3 is all < 1 (paste shows 20/10 and 200/100, due to incremental
> Relevant code from here is
>     if (Sets.intersection(l1overlapping, compacting).size() > 0)
>         return Collections.emptyList();
> Since there will be overlap between what is compacting and L1 (in my case, pushing over
1,000 tables in to L1 from L0 SCTS), I get a pile up of 1,000 smaller tables in L0 while awaiting
the transition from L0 to L1 and destroy my performance.
> Requested outcome is to continue to perform SCTS on non-compacting L0 tables.

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