Hello Martin If, and only if you have RF=1, single partition mutations (including batches) are isolated.
Otherwise, with RF>1, even a simple UPDATE is not isolated because one client can read the updated value on one replica and another client reads the old value on another replica On Mon, May 18, 2015 at 12:32 PM, Martin Krasser <krass...@googlemail.com> wrote: > Hello, > > I have an application that inserts multiple rows within a single partition > (= all rows share the same partition key) using a BATCH statement. Is it > possible that other clients can partially read that batch or is the batch > application isolated i.e. other clients can only read all rows of that > batch or none of them? > > I understand that a BATCH update to multiple partitions is not isolated > but I'm not sure if this is also the case for a single partition: > > - The article Atomic batches in Cassandra 1.2 > <http://www.datastax.com/dev/blog/atomic-batches-in-cassandra-1-2> says > that *"... we mean atomic in the database sense that if any part of the > batch succeeds, all of it will. No other guarantees are implied; in > particular, there is no isolation"*. > > - On the other hand, the CQL BATCH > <https://cassandra.apache.org/doc/cql3/CQL.html#batchStmt> docs at > cassandra.apache.org mention that *"* *... the [batch] operations are > still only isolated within a single partition"* which is a clear > statement but doesn't it contradict the previous and the next one? > > - The CQL BATCH > <http://docs.datastax.com/en/cql/3.1/cql/cql_reference/batch_r.html> docs > at docs.datastax.com mention that *"... there is no batch isolation. > Clients are able to read the first updated rows from the batch, while other > rows are still being updated on the server. However, transactional row > updates within a partition key are isolated: clients cannot read a partial > update"*. Also, what does *"transactional row updates"* mean in this > context? A lightweight transaction? Something else? > > Thanks for any help, > Martin > >
