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From Stefano Ortolani <ostef...@gmail.com>
Subject Re: LeveledCompactionStrategy
Date Tue, 26 May 2015 14:36:25 GMT
Hi Jean,

I am trying to solve a similar problem here. I would say that the only
deterministic way is to rebuild the SStable of that column family via
nodetool scrub.

Otherwise you'd need to :
* decrease tombstone_threshold
* wait for gc_grace_time

Cheers,
Stefano



On Tue, May 26, 2015 at 12:51 PM, Jean Tremblay <
jean.tremblay@zen-innovations.com> wrote:

>  I played around with these settings, namely the tombstone_threshold, and
> it **eventually** triggered a Tombstone Compaction.
> Now I see that getting rid of these Tombstone is a process which takes
> some times.
>
>  I would like to be able to schedule a Tombstone Compaction.
>
>  Is there a way to trigger immediately a Tombstone Compaction on a table
> which is using LeveledCompactionStrategy?
>
>
>  Thanks a lot for your help
>
>  Jean
>
>  On 14 May 2015, at 22:45 , Nate McCall <nate@thelastpickle.com> wrote:
>
>  You can make LCS more aggressive with tombstone-only compactions via
> seting unchecked_tombstone_compaction=true and turn down
> tombstone_threshold to 0.05 (maybe going up or down as needed). Details on
> both can be found here:
> http://docs.datastax.com/en/cql/3.1/cql/cql_reference/compactSubprop.html
>
>  As for monitoring tombstones, there is a "tombstoneScannedHistogram" on
> ColumnFamilyMetrics which measures how many tombstones were discarded
> during reads.
>
>  Also, you should take a couple of SSTables from production and use the
> sstablemetadata utility specifically looking at "Estimated droppable
> tombstones" and "Estimated tombstone drop times" output from such.
>
>  Spend some time experimenting with those settings incrementally. Finding
> the sweet spot is different for each workload will make a huge difference
> in overall performance.
>
>
>
> On Thu, May 14, 2015 at 8:06 AM, Jean Tremblay <
> jean.tremblay@zen-innovations.com> wrote:
> >
> > Hi,
> >
> > I’m using Cassandra 2.1.4 with a table using LeveledCompactionStrategy.
> > Often I need to delete many rows and I want to make sure I don’t have
> too many tombstones.
> >
> > How does one get rid of tombstones in a table using LCS?
> > How can we monitor how many tombstones are around?
> >
> > Thanks for your help.
> >
> > Jean
>
>
>
>
> --
> -----------------
> Nate McCall
> Austin, TX
> @zznate
>
> Co-Founder & Sr. Technical Consultant
> Apache Cassandra Consulting
> http://www.thelastpickle.com
>
>
>

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