Mailing-List: contact commits-help@cassandra.apache.org; run by ezmlm
Precedence: bulk
Reply-To: dev@cassandra.apache.org
Date: Wed, 29 Aug 2012 04:26:07 +1100 (NCT)
From: "Edward Capriolo (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
Message-ID: <1447755820.7225.1346174768010.JavaMail.jiratomcat@arcas>
In-Reply-To: <1774763565.37924.1345592798104.JavaMail.jiratomcat@arcas>
Subject: [jira] [Commented] (CASSANDRA-4565) TTL columns with older then
 gcgrace do not need to flush
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit


    [ https://issues.apache.org/jira/browse/CASSANDRA-4565?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13443295#comment-13443295 ] 

Edward Capriolo commented on CASSANDRA-4565:
--------------------------------------------

 I noticed this because the method I added had loggers that I never saw in the output.  What I saw happening was ExpiringColumns past TTL never made it into the flush. After some tracing I came to the conclusion that maybeResetDeletionTimes takes into account ttl time, and converts them to DeletedColumns which do not get flushed. 

Also if you take the unit test I added, it passes without modification to the code base so unless my test is not doing what I think it seems like cassandra is already handling this. 

If you are finding this not to be the case we can re-open and I will take a look. 
                
> TTL columns with older then gcgrace do not need to flush
> --------------------------------------------------------
>
>                 Key: CASSANDRA-4565
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4565
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Edward Capriolo
>            Assignee: Edward Capriolo
>             Fix For: 1.3
>
>         Attachments: cassandra-4565.patch.1.txt
>
>
> With memcache many people are willing to sacrifice durability for performance. Cassandra has a TimeToLive feature that can be used in caching scenarios with low values for gc_grace_seconds. However from a code dive it seems that cassandra will always write TTL to disk, even those that are beyond gc_grace_seconds. If a use case very large memtables,small ttl, and small gc_grace it is possible that flushing these columns to disk can be skipped entirely in some scenarios. 

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira