There is setting in the cassandra.yaml file which controls that.
# Whether or not a snapshot is taken of the data before keyspace truncation # or dropping of column families. The STRONGLY advised default of true # should be used to provide data safety. If you set this flag to false, you will # lose data on truncation or drop. auto_snapshot: true ----- Original Message ----- From: "Víctor Hugo Oliveira Molinar" <vhmoli...@gmail.com> To: user@cassandra.apache.org Sent: Tuesday, March 19, 2013 11:50:35 AM Subject: Truncate behaviour Hello guys! I'm researching the behaviour for truncate operations at cassandra. Reading the oficial wiki page( http://wiki.apache.org/cassandra/API ) we can understand it as: "Removes all the rows from the given column family." And reading the DataStax page( http://www.datastax.com/docs/1.0/references/cql/TRUNCATE ) we can understand it as: " A TRUNCATE statement results in the immediate, irreversible removal of all data in the named column family." But I think there is a missing and important point about truncate operations. At least at 1.2.0 version, whenever I run a truncate operation, C* automatically creates a snapshot file of the column family, resulting in a fake free disk space. I'm intentionally mentioning 'fake free disk space' because I only figured it out when the machine disk space was at high usage. - Is it a security C* behaviour of creating snapshots for each CF before truncate operation? - In my scenario I need to purge my column family data every day. I thought that truncate could handle it based at the docs. But it doesnt. And since I dont want to manually delete those snapshots, I'd like to know if there is a safe and practical way to perform a daily purge of this CF data. Thanks in advance!
