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From "Sylvain Lebresne (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-2620) Don't persist TTL for expiring columns
Date Mon, 09 May 2011 12:00:03 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-2620?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13030696#comment-13030696
] 

Sylvain Lebresne commented on CASSANDRA-2620:
---------------------------------------------

Right now, if you need to know when a column c will expire, you'll compute c.timestamp + c.ttl.
That code will break if you change the meaning of the ttl field. Remark that I never pretended
this cannot be done with a delta TTL, it's even more direct. What I'm saying however is that
making the change will make the update potentially painful and very error prone (it would
be easy to forget to make the change in the client code, or even to forget to update one or
two places).

> Don't persist TTL for expiring columns
> --------------------------------------
>
>                 Key: CASSANDRA-2620
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2620
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Stu Hood
>            Priority: Minor
>             Fix For: 1.0
>
>
> We persist both the TTL (5 seconds from now) and the localExpirationTime (the local time
at +5 seconds) for expiring columns, but the TTL is never used again, except when we return
expiring columns to clients.
> Rather than storing the TTL to return to clients, we could calculate a delta TTL value
by subtracting the current time from the localExpirationTime, and save 4 bytes on disk.

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