I have read that blog post which actually was the source of the initial confusion ;)
If I write normally (no batch) at Quorum, then a hinted write wouldn’t count as a valid write so the write wouldn’t succeed, which means I would have to retry. That’s a pretty well defined outcome. Now if I write a logged batch at Quorum, then a by definition, a hinted write shouldn’t be considered a valid response, no? - Drew On Mar 17, 2014, at 11:23 AM, Jonathan Lacefield <jlacefi...@datastax.com> wrote: > Hello, > > Have you seen this blog post, it's old but still relevant. I think it will > answer your questions. > http://www.datastax.com/dev/blog/atomic-batches-in-cassandra-1-2. > > I think the answer lies in how Cassandra defines a batch "In the context of > a Cassandra batch operation, atomic means that if any of the batch succeeds, > all of it will." > > My understanding is that in your scenario if either statement succeeded, > you batch would succeed. So #1 would get "hinted" and #2 would be applied, > assuming no other failure events occur, like the coordinator fails, the > client fails, etc. > > Hope that helps. > > Thanks, > > Jonathan > > Jonathan Lacefield > Solutions Architect, DataStax > (404) 822 3487 > > > > > > > On Mon, Mar 17, 2014 at 1:38 PM, Drew Kutcharian <d...@venarc.com> wrote: > 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 >> > >
