cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Alain RODRIGUEZ <arodr...@gmail.com>
Subject Re: ALTER default_time_to_live
Date Thu, 18 Jan 2018 11:32:01 GMT
>
> I set  default_time_to_live for existing table. Does it affect existing
> data?


No, it sets a default TTL for the future writes (that is no guarantee, as
it can be overwritten in any specific query).

It seems data to be deleted, but after compaction, I don't see any disk
> space freed as expected


Indeed tombstones are responsible for tombstones eviction, yet there are
some conditions to respect to be able to remove the tombstones (for
consistency reasons). I detailed this last year, and even though the
content is a bit old, main principles are still true and the tuning options
are still relevant.

*About deletes and tombstones: *
http://thelastpickle.com/blog/2016/07/27/about-deletes-and-tombstones.html

*tl;dr: *I would give a try to *unchecked_tombstone_compaction: true*.
Maybe also consider using TWCS because of this "TTL is also ten days on one
table and 100 days on other.". But I really recommend you to understand how
this all work to act wisely. My guess can be wrong.

*About TWCS*: http://thelastpickle.com/blog/2016/12/08/TWCS-part1.html

C*heers,
-----------------------
Alain Rodriguez - @arodream - alain@thelastpickle.com
France / Spain

The Last Pickle - Apache Cassandra Consulting
http://www.thelastpickle.com

2018-01-18 11:15 GMT+00:00 Vlad <qa23d-vvd@yahoo.com.invalid>:

> Hi,
>
> I set  default_time_to_live for existing table. Does it affect existing
> data? It seems data to be deleted, but after compaction, I don't see any
> disk space freed as expected. Database has data for almost year, GC time is
> ten days, and TTL is also ten days on one table and 100 days on other.
>
>  Cassandra version 3.11.0
>
> Thanks.
>

Mime
View raw message