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https://issues.apache.org/jira/browse/CASSANDRA-4341?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jonathan Ellis updated CASSANDRA-4341:
--------------------------------------
Attachment: 4341.txt
Patch attached with the following approach:
{noformat}
. // We treat L0 compactions specially:
// 1a. add sstables to the candidate set until we have at least
maxSSTableSizeInMB
// 1b. prefer choosing older sstables as candidates, to newer ones
// 1c. any L0 sstables that overlap a candidate, will also become
candidates
// 2. At most MAX_COMPACTING_L0 sstables will be compacted at once
// 3. If total candidate size is less than maxSSTableSizeInMB, we
won't bother compacting with L1,
// and the result of the compaction will stay in L0 instead of
being promoted (see promote())
{noformat}
> Small SSTable Segments Can Hurt Leveling Process
> ------------------------------------------------
>
> Key: CASSANDRA-4341
> URL: https://issues.apache.org/jira/browse/CASSANDRA-4341
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Affects Versions: 1.0.0
> Reporter: Benjamin Coverston
> Labels: compaction
> Fix For: 1.1.2
>
> Attachments: 4341.txt
>
>
> This concerns:
> static int MAX_COMPACTING_L0 = 32;
> Repair can create very small SSTable segments. We should consider moving to a
> threshold that takes into account the size of the files brought into
> compaction rather than the number of files for this and similar situations.
> Bringing the small files from L0 to L1 magnifies the issue.
> If there are too many very small files in L0 perhaps even an intermediate
> compaction would even reduce the magnifying effect of a L0 to L1 compaction.
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