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From Sylvain Lebresne <sylv...@yakaz.com>
Subject Re: Cassandra and TTL
Date Thu, 14 Jan 2010 10:17:12 GMT
On Thu, Jan 14, 2010 at 6:46 AM, August Zajonc <augustz@augustz.com> wrote:
> I personally like this last option of expiring entire sstables. It seems
> significantly more efficient then scrubbing data. The granularity might be a
> bit high, but by columnfamily seems a reasonable trade-off in the short run
> for an easier solution.
>
> For apps that don't want to see the old data, during a read if the data had
> a timestamp older than the expire time on the ColumnFamily it could also be
> ignored, then when all in an sstable < x, truncate.
>
> Logs are a great example of this.

I personally think that truncate and a potential TTL are two different
things, since as
you said, they have very different granularity. In particular, using
truncate basically
means that all the data in the CF you truncate have exactly the same
TTL. Plus,
you have to know if a data have a TTL (and which one if you want
different CF that you
truncate at different time) when you request it. I, for one, have many
use where it's not
really a desirable solution. Plus, truncate suppose that you
deactivate compaction for
you CF, which may or may not be affordable.
But sure, for some models, and logs are a great example indeed,
truncate will be the
perfect solution.

Anyway, I'm starting to seriously consider giving this TTL idea a
shot. We'll see how
that goes.

--
Sylvain

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