Hi Jonathan, I’m still a bit unclear on this. Say I have two CQL3 tables: - user (replication of 3) - user_email_index (replication of 3)
Now I create a new logged batch at quorum consistency level and put two inserts in there: #1 Insert into the “user" table with partition key of a timeuuid of the user #2 Insert into the “user_email_index" with partition key of user’s email address As you can see, there is a chance that these two insert statements will be executed on two different nodes because they are keyed by different partition keys. So based on the docs for Logged Batches, a batch will be applied “eventually” in an "all or nothing” fashion. So my question is, what happens if insert #1 fails (say replicas are unavailable), would insert #2 get applied? Would the whole thing be rejected and return an error to the client? PS. I’m aware of the isolation guarantees and that’s not an issue. All I need to make sure is that if the first the statement failed, the whole batch needs to fail. Thanks, Drew On Mar 17, 2014, at 5:33 AM, Jonathan Lacefield <jlacefi...@datastax.com> wrote: > Hello, > > Consistency is declared at the statement level, i.e. batch level when > writing, but enforced at each batch row level. My understanding is that each > batch (and all of it's contents) will be controlled through a specific CL > declaration. So batch A could use a CL of QUORUM while batch B could use a > CL of ONE. > > The detail that may help sort this out for you is that batch statements do > not provide isolation guarantees: > www.datastax.com/documentation/cql/3.0/cql/cql_reference/batch_r.html. This > means that you write the batch as a batch but the reads are per row. If you > are reading records contained in the batch, you will read results of > partially updated batches. Taking this into account for your second > question, you should expect that your read CL will preform as it would for > any individual row mutation. > > Hope this helps. > > Jonathan > > Jonathan Lacefield > Solutions Architect, DataStax > (404) 822 3487 > > > > > > > On Sat, Mar 15, 2014 at 12:23 PM, Drew Kutcharian <d...@venarc.com> wrote: > Hi Guys, > > How do Atomic Batches and Consistency Level relate to each other? More > specifically: > > - Is consistency level set/applicable per statement in the batch or the batch > as a whole? > > - Say if I write a Logged Batch at QUORUM and read it back at QUORUM, what > can I expect at normal, single node replica failure or double node replica > failure scenarios? > > Thanks, > > Drew >
