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Posted to commits@cassandra.apache.org by "Yuki Morishita (Updated) (JIRA)" <ji...@apache.org> on 2011/11/20 22:55:52 UTC

[jira] [Updated] (CASSANDRA-3442) TTL histogram for sstable metadata

     [ https://issues.apache.org/jira/browse/CASSANDRA-3442?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Yuki Morishita updated CASSANDRA-3442:
--------------------------------------

    Attachment: 3442.txt

Patch is against 1.0 branch. Added TTL histogram and logic to determine whether to perform compaction over sstables that have expiring columns more than threshold.
Threshold is default to 20% (0.2) but you can specify via compaction_strategy_options. 

                
> 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: Yuki Morishita
>            Priority: Minor
>              Labels: compaction
>         Attachments: 3442.txt
>
>
> 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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