Hello Gabriel, Sorry for not answering earlier. I should have, given that I contributed spreading this wrong idea. I will also try to edit my comment in the post. I have been fooled by the piece of documentation you mentioned when answering this question on our blog. I probably answered this one too quickly, even though I wrote this a thing 'to explore', even saying I did not try it explicitely.
Another clue to explore would be to use the TTL as a default value if > that's a good fit. TTLs set at the table level with > 'default_time_to_live' **should not generate any tombstone at all in > C*3.0+**. Not tested on my hand, but I read about this. So my sentence above is wrong. Basically, the default can be overwritten by the TTL at the query level and I do not see how Cassandra could handle this without tombstones. I spent time on the post and it was reviewed. I believe it is reliable. The questions, on the other side, are answered by me alone and well, that only reflects my opinion at the moment I am asked and I sometimes find enough time and interest to dig topics, sometimes a bit less. So this is fully on me, my apologies for this inaccuracy. I must say am always afraid when writing publicly and sharing information to do this kind of mistakes and mislead people. I hope the impact of this read was still positive for you overall. >From the example I conclude that isn't true that `default_time_to_live` not > require tombstones, at least for version 3.0.13. > Also, I am glad to see you did not believe me or Datastax documentation but tried it by yourself. This is definitively the right approach. But how would C* delete without tombstones? Why this should be a different > scenario to using TTL per insert? > Yes, exactly this, C*heers. ----------------------- Alain Rodriguez - @arodream - al...@thelastpickle.com France / Spain The Last Pickle - Apache Cassandra Consulting http://www.thelastpickle.com Le lun. 17 sept. 2018 à 14:58, Gabriel Giussi <gabrielgiu...@gmail.com> a écrit : > > From > https://docs.datastax.com/en/cassandra/3.0/cassandra/dml/dmlAboutDeletes.html > > > Cassandra allows you to set a default_time_to_live property for an > entire table. Columns and rows marked with regular TTLs are processed as > described above; but when a record exceeds the table-level TTL, **Cassandra > deletes it immediately, without tombstoning or compaction**. > > This is also answered in https://stackoverflow.com/a/50060436/3517383 > > > If a table has default_time_to_live on it then rows that exceed this > time limit are **deleted immediately without tombstones being written**. > > And commented in LastPickle's post About deletes and tombstones ( > http://thelastpickle.com/blog/2016/07/27/about-deletes-and-tombstones.html#comment-3949581514 > ) > > > Another clue to explore would be to use the TTL as a default value if > that's a good fit. TTLs set at the table level with 'default_time_to_live' > **should not generate any tombstone at all in C*3.0+**. Not tested on my > hand, but I read about this. > > I've made the simplest test that I could imagine using > `LeveledCompactionStrategy`: > > CREATE KEYSPACE IF NOT EXISTS temp WITH replication = {'class': > 'SimpleStrategy', 'replication_factor': '1'}; > > CREATE TABLE IF NOT EXISTS temp.test_ttl ( > key text, > value text, > PRIMARY KEY (key) > ) WITH compaction = { 'class': 'LeveledCompactionStrategy'} > AND default_time_to_live = 180; > > 1. `INSERT INTO temp.test_ttl (key,value) VALUES ('k1','v1');` > 2. `nodetool flush temp` > 3. `sstabledump mc-1-big-Data.db` > [image: cassandra0.png] > > 4. wait for 180 seconds (default_time_to_live) > 5. `sstabledump mc-1-big-Data.db` > [image: cassandra1.png] > > The tombstone isn't created yet > 6. `nodetool compact temp` > 7. `sstabledump mc-2-big-Data.db` > [image: cassandra2.png] > > The **tombstone is created** (and not dropped on compaction due to > gc_grace_seconds) > > The test was performed using apache cassandra 3.0.13 > > From the example I conclude that isn't true that `default_time_to_live` > not require tombstones, at least for version 3.0.13. > However this is a very simple test and I'm forcing a major compaction with > `nodetool compact` so I may not be recreating the scenario where > default_time_to_live magic comes into play. > > But how would C* delete without tombstones? Why this should be a different > scenario to using TTL per insert? > > This is also asked at stackoverflow > <https://stackoverflow.com/questions/52282517/how-default-time-to-live-would-delete-rows-without-tombstones-in-cassandra> >
