Hi Everyone, I was reading a blog on TWCS by Alex Dejanovski from The Last Pickle ( http://thelastpickle.com/blog/2016/12/08/TWCS-part1.html)
When I got to the comments section, I didn't understand why setting gc_grace_seconds to 0 will disable hints for the associated table: *"It is a very good point that gc_grace_seconds shouldn't be lowered too much as its impact on hinted handoff is not a well known fact, and using a value of 0 will purely disable hints on the table."* When I tried to read some more about deletes and TTLs, I got to a Datastax documentation https://docs.datastax.com/en/cassandra/3.0/cassandra/dml/dmlAboutDeletes.html stating the following: *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.* Which got me a bit more confused. So I hope someone can shed some light on some questions I've got: - Why setting gc_grace_seconds=0 will disable hints for the table? - How can an expired TTL record be deleted by Cassandra without tombstoning or compaction? Aren't SSTables immutable files, and expired records are removed through compaction? - If I only use TTL for deletion, do I still need gc_grace_seconds to be bigger than 0? - If I only use TTL for deletion, but use updates as well, do I need gc_grace_seconds to be bigger than 0? Sorry for all those questions, I'm just really confused from all the TTL/tombstones subject (still a newbie). Thanks a lot! Shalom Sagges DBA T: +972-74-700-4035 <http://www.linkedin.com/company/164748> <http://twitter.com/liveperson> <http://www.facebook.com/LivePersonInc> We Create Meaningful Connections -- This message may contain confidential and/or privileged information. If you are not the addressee or authorized to receive this on behalf of the addressee you must not use, copy, disclose or take action based on this message or any information herein. If you have received this message in error, please advise the sender immediately by reply email and delete this message. Thank you.
