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https://issues.apache.org/jira/browse/CASSANDRA-4153?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13254250#comment-13254250
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Jonathan Ellis commented on CASSANDRA-4153:
-------------------------------------------

bq. truncate does not need to flush memtables to disk when snapshots are 
disabled

It still needs to clear out the memtables somehow though, or truncate won't 
actually discard all the data it's expected to.
                
> Optimize truncate when snapshots are disabled or keyspace not durable
> ---------------------------------------------------------------------
>
>                 Key: CASSANDRA-4153
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4153
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Christian Spriegel
>            Priority: Minor
>         Attachments: OptimizeTruncate_v1.diff
>
>
> My goal is to make truncate to be less IO intensive so that my junit tests 
> run faster (as already explained in CASSANDRA-3710). I think I have now a 
> solution which does not change too much:
> I created a patch that optimizes three things within truncate:
> - Skip the whole Commitlog.forceNewSegment/discardCompletedSegments, if 
> durable_writes are disabled for the keyspace.
> - With CASSANDRA-3710 implemented, truncate does not need to flush memtables 
> to disk when snapshots are disabled.
> - Reduce the sleep interval
> The patch works nicely for me. Applying it and disabling 
> durable_writes/autoSnapshot increased the speed of my testsuite vastly. I 
> hope I did not overlook something.
> Let me know if my patch needs cleanup. I'd be glad to change it, if it means 
> the patch will get accepted.

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