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https://issues.apache.org/jira/browse/CASSANDRA-5546?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sylvain Lebresne reassigned CASSANDRA-5546:
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Assignee: Sylvain Lebresne
> Gc_grace should start at the creation of the column, not when it expires
> ------------------------------------------------------------------------
>
> Key: CASSANDRA-5546
> URL: https://issues.apache.org/jira/browse/CASSANDRA-5546
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Sylvain Lebresne
> Assignee: Sylvain Lebresne
> Fix For: 3.x
>
>
> Currently, gc_grace determines "the minimum time we keep a column that has
> been marked for deletion", where "marked for deletion" is creation time for a
> DeletedColumn or the expiration time for an ExpiringColumn.
> However, in the case of expiring columns, if you want to optimize deletions
> while making sure you don't resurrect overwritten data, you only care about
> keeping expired columns gc_grace seconds *since their creation time*, not
> *since their expiration time*. It would thus be better to have gc_grace be
> "the minimum time we keep a column since it's creation" (which would change
> nothing for tombstones, but for TTL would basically ensure we remove the
> expiration time from the time we keep the column once expired).
> To sum it up, this would have the following advantages:
> # This will make fine tuning of gc_grace a little less of a black art.
> # This will be more efficient for CF mixing deletes and expiring columns
> (we'll remove tombstones for the expiring one sooner).
> # This means gc_grace will be more reliable for things like CASSANDRA-5314.
> Doing this is pretty simple. The one concern is backward compatilibity: it
> means people that have fine tuned gc_grace to a very low value because they
> knew it was ok due to their systematic use of ttls might have to update it
> back to a bigger, more reasonable value before updates.
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