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From Nate McCall <n...@thelastpickle.com>
Subject Re: LeveledCompactionStrategy
Date Thu, 14 May 2015 20:45:19 GMT
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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