cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From John Sanda <john.sa...@gmail.com>
Subject Re: manual deletes with TWCS
Date Fri, 05 May 2017 21:04:40 GMT
This is involving TTLed data, and I actually would want to delete all
related partitions across all time windows. Let's say I have a time series
partitioned by day with a 7 day TTL and a window size of one day. If I
delete partitions for the past seven days, would I still run into the issue
of data purge being postponed?

On Fri, May 5, 2017 at 4:57 PM, Jon Haddad <jonathan.haddad@gmail.com>
wrote:

> You cannot.
>
> From Alex’s TLP post: http://thelastpickle.com/blog/2016/12/08/TWCS-
> part1.html
>
> TWCS is no fit for workload that perform deletes on non TTLed data.
> Consider that SSTables from different time windows will never be compacted
> together, so data inserted on day 1 and deleted on day 2 will have the
> tombstone and the shadowed cells living in different time windows. Unless a
> major compaction is performed (which shouldn’t), and while the deletion
> will seem effective when running queries, space will never be reclaimed on
> disk.
> Deletes can be performed on TTLed data if needed, but the partition will
> then exist in different time windows, which will postpone actual deletion
> from disk until both time windows fully expire.
>
>
> On May 5, 2017, at 1:54 PM, John Sanda <john.sanda@gmail.com> wrote:
>
> How problematic is it to perform deletes when using TWCS? I am currently
> using TWCS and have some new use cases for performing deletes. So far I
> have avoided performing deletes, but I am wondering what issues I might run
> into.
>
>
> - John
>
>
>


-- 

- John

Mime
View raw message