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https://issues.apache.org/jira/browse/CASSANDRA-3442?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13142006#comment-13142006
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Sylvain Lebresne commented on CASSANDRA-3442:
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I think the idea has merits.
We have to keep in mind that unless the expired data is also gcable, this would
only transform expiring columns to tombstones, so for those that have very
small columns (~4 bytes) this would be useless. I would also maybe bump that
20% up to be sure we don't rewrite too ofen sstables that are good candidate
for compaction anyway. But on principle this is a good idea I believe.
> TTL histogram for sstable metadata
> ----------------------------------
>
> Key: CASSANDRA-3442
> URL: https://issues.apache.org/jira/browse/CASSANDRA-3442
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Jonathan Ellis
> Assignee: Sylvain Lebresne
> Priority: Minor
> Labels: compaction
>
> Under size-tiered compaction, you can generate large sstables that compact
> infrequently. With expiring columns mixed in, we could waste a lot of space
> in this situation.
> If we kept a TTL EstimatedHistogram in the sstable metadata, we could do a
> single-sstable compaction aginst sstables with over 20% (?) expired data.
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