This is incorrect, there's no optimization used that references the table level TTL setting. The max local deletion time is stored in table metadata. See org.apache.cassandra.io.sstable.metadata.StatsMetadata#maxLocalDeletionTime in the Cassandra 3.0 branch. The default ttl is stored here: org.apache.cassandra.schema.TableParams#defaultTimeToLive and is never referenced during compaction.
Here's an example from a table I created without a default TTL, you can use the sstablemetadata tool to see: jhaddad@rustyrazorblade ~/dev/cassandra/data/data/test$ ../../../tools/bin/sstablemetadata a-7bca6b50e8a511e6869a5596edf4dd35/mc-1-big-Data.db ..... SSTable max local deletion time: 1485980862 On Wed, Feb 1, 2017 at 6:59 AM DuyHai Doan <doanduy...@gmail.com> wrote: > Global TTL is better than dynamic runtime TTL > > Why ? > > Because Global TTL is a table property and Cassandra can perform > optimization when compacting. > > For example if it can see than the maxTimestamp of an SSTable is older > than the table Global TTL, the SSTable can be entirely dropped during > compaction > > Using dynamic TTL at runtime, since Cassandra doesn't how and cannot track > each individual TTL value, the previous optimization is not possible (even > if you always use the SAME TTL for all query, Cassandra is not supposed to > know that) > > > > On Wed, Feb 1, 2017 at 3:01 PM, Cogumelos Maravilha < > cogumelosmaravi...@sapo.pt> wrote: > > Thank you all, for your answers. > > On 02/01/2017 01:06 PM, Carlos Rolo wrote: > > To reinforce Alain statement: > > "I would say that the unsafe part is more about using C* 3.9" this is key. > You would be better on 3.0.x unless you need features on the 3.x series. > > Regards, > > Carlos Juzarte Rolo > Cassandra Consultant / Datastax Certified Architect / Cassandra MVP > > Pythian - Love your data > > rolo@pythian | Twitter: @cjrolo | Skype: cjr2k3 | Linkedin: > *linkedin.com/in/carlosjuzarterolo > <http://linkedin.com/in/carlosjuzarterolo>* > Mobile: +351 918 918 100 <+351%20918%20918%20100> > www.pythian.com > > On Wed, Feb 1, 2017 at 8:32 AM, Alain RODRIGUEZ <arodr...@gmail.com> > wrote: > > Is it safe to use TWCS in C* 3.9? > > > I would say that the unsafe part is more about using C* 3.9 than using > TWCS in C*3.9 :-). I see no reason to say 3.9 would be specifically unsafe > in C*3.9, but I might be missing something. > > Going from STCS to TWCS is often smooth, from LCS you might expect an > extra load compacting a lot (all?) of the SSTable from what we saw from the > field. In this case, be sure that your compaction options are safe enough > to handle this. > > TWCS is even easier to use on C*3.0.8+ and C*3.8+ as it became the new > default replacing TWCS, so no extra jar is needed, you can enable TWCS as > any other default compaction strategy. > > C*heers, > ----------------------- > Alain Rodriguez - @arodream - al...@thelastpickle.com > France > > The Last Pickle - Apache Cassandra Consulting > http://www.thelastpickle.com > > 2017-01-31 23:29 GMT+01:00 Cogumelos Maravilha <cogumelosmaravi...@sapo.pt > >: > > Hi Alain, > > Thanks for your response and the links. > > I've also checked "Time series data model and tombstones". > > Is it safe to use TWCS in C* 3.9? > > Thanks in advance. > > On 31-01-2017 11:27, Alain RODRIGUEZ wrote: > > Is there a overhead using line by line option or wasted disk space? > > There is a very recent topic about that in the mailing list, look for "Time > series data model and tombstones". I believe DuyHai answer your question > there with more details :). > > *tl;dr:* > > Yes, if you know the TTL in advance, and it is fixed, you might want to go > with the table option instead of adding the TTL in each insert. Also you > might want consider using TWCS compaction strategy. > > Here are some blogposts my coworkers recently wrote about TWCS, it might > be useful: > > http://thelastpickle.com/blog/2016/12/08/TWCS-part1.html > http://thelastpickle.com/blog/2017/01/10/twcs-part2.html > > C*heers, > ----------------------- > Alain Rodriguez - @arodream - al...@thelastpickle.com > France > > The Last Pickle - Apache Cassandra Consulting > http://www.thelastpickle.com > > > > 2017-01-31 10:43 GMT+01:00 Cogumelos Maravilha <cogumelosmaravi...@sapo.pt > >: > > Hi I'm just wondering what option is fastest: > > Global:*create table xxx (.....**AND **default_time_to_live = **XXX**;** > and**UPDATE xxx USING TTL XXX;* > > Line by line: > *INSERT INTO xxx (...** USING TTL xxx;* > > Is there a overhead using line by line option or wasted disk space? > > Thanks in advance. > > > > > >
