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From Kévin LOVATO <>
Subject TTL and gc_grace_period
Date Fri, 05 Jun 2015 15:30:25 GMT

I have a column family with data (metrics) that is never overwritten and
only deleted using TTLs, and I am wondering if it would be reasonable to
have a very low gc_grace_period (even 0) on that CF. I would like to do
that mainly to save space and also to prevent tombstone scanning.

>From what I understand of what I could read online, when an expired TTLed
column is compacted, it is replaced by a tombstone, so having
gc_grace_period would prevent that. Although this would allow the
appearance of ghost/zombie columns.

The question I'm trying to answer here is the following: Would those ghost
columns be able to appear, and if so, would it be a problem, since they
would themselves be marked as "expired"?



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