Re: Compaction does not remove tombstones if column has higher TTL

[Ken Hancock <ke...@schange.com>]

I agree, that's totally unintuitive.  I would have the same expectations
that compaction is done on a row/column pair instead of simply at the row
level.


On Fri, Feb 28, 2014 at 11:44 AM, Keith Wright <kw...@nanigans.com> wrote:

> FYI - I recently filed
> https://issues.apache.org/jira/browse/CASSANDRA-6654 and wanted to let
> everyone know the result as it was not what I expected.   I am using C*
> 1.2.12 and found that my droppable tombstone ratio kept increasing on an
> LCS table (currently > .3).  Documentation states that compactions should
> be triggered when that gets above .2 to help cleanup tombstones and in my
> case compactions are definitely not running behind.
>
> I am setting different TTLs on different columns (this capability was one
> of the things I love about Cassandra) and the result of the ticket is that
> only columns whose write time is less than now + the MAX TTL of columns
> within the row will NOT be removed.  In my case, I was setting some columns
> to 6 months and others to 7 days so this meant that the 7 day data will in
> fact NOT be removed until 6 months!  This results in MUCH wider rows than I
> expected.
>
> It appears that this was likely fixed in 2.1 but obviously people will not
> be deploying that to production anytime soon.  It appears that I will just
> have to no longer set the 6 month TTL and instead leave it as forever to
> ensure that the smaller TTLs are respected.  This is an acceptable tradeoff
> for me since the 7 day columns are the ones that get much larger (against a
> map column type).
>
> So be warned, mixing TTLs in a row does not appear to result in the data
> being compacted away.
>
> Thanks
>



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