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From "T Jake Luciani (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-5371) Perform size-tiered compactions in L0
Date Thu, 04 Apr 2013 02:02:13 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-5371?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13621653#comment-13621653
] 

T Jake Luciani commented on CASSANDRA-5371:
-------------------------------------------

Oh good, this is what I wanted the implementation to end up being.

In LeveledManifest.getCompactionCandidates:

I think there is a bug in the size tier candidate checks.  You seem to be size tiering across
all the non-compacting sstables and not the level0 ones.  I think you mean't to intersect
the level0 sstables with the non-compacting ones.  You should also add a check after that
to make sure the non-compacting level0 sstables are still > MAX_COMPACTING_L0

Also, the code only checks for STCS when a higher level is ready to be compacted.  Maybe move
this to the top before the higher level checks. We know the higher levels are seek bounded
but the code should try to keep up with level 0 flushes as much as possible.
                
> Perform size-tiered compactions in L0
> -------------------------------------
>
>                 Key: CASSANDRA-5371
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-5371
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>            Reporter: Jonathan Ellis
>            Assignee: Jonathan Ellis
>             Fix For: 2.0
>
>         Attachments: HybridCompactionStrategy.java
>
>
> If LCS gets behind, read performance deteriorates as we have to check bloom filters on
man sstables in L0.  For wide rows, this can mean having to seek for each one since the BF
doesn't help us reject much.
> Performing size-tiered compaction in L0 will mitigate this until we can catch up on merging
it into higher levels.

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