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https://issues.apache.org/jira/browse/CASSANDRA-13561?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jeff Jirsa reassigned CASSANDRA-13561:
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Assignee: Andrew Whang
> Purge TTL on expiration
> -----------------------
>
> Key: CASSANDRA-13561
> URL: https://issues.apache.org/jira/browse/CASSANDRA-13561
> Project: Cassandra
> Issue Type: New Feature
> Reporter: Andrew Whang
> Assignee: Andrew Whang
> Priority: Minor
> Fix For: 4.0
>
>
> Tables with mostly TTL columns tend to suffer from high droppable tombstone
> ratio, which results in higher read latency, cpu utilization, and disk usage.
> Expired TTL data become tombstones, and the nature of purging tombstones
> during compaction (due to checking for overlapping SSTables) make them
> susceptible to surviving much longer than expected. A table option to purge
> TTL on expiration would address this issue, by preventing them from becoming
> tombstones. A boolean purge_ttl_on_expiration table setting would allow users
> to easily turn the feature on or off.
> Being more aggressive with gc_grace could also address the problem of long
> lasting tombstones, but that would affect tombstones from deletes as well.
> Even if a purged [expired] cell is revived via repair from a node that hasn't
> yet compacted away the cell, it would be revived as an expiring cell with the
> same localDeletionTime, so reads should properly handle them. As well, it
> would be purged in the next compaction.
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