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