Thanks DuyHai for the info. I already see this JIRA, however the use case I describe is slightly different from the JIRA as there is only ONE condition on ONE table. Other statements of the batch does not have any condition. So I guess in that case the Paxos operation does not span multiple table but operates only the table that has the condition. Am I wrong?
2016-10-24 10:21 GMT+02:00 DuyHai Doan <doanduy...@gmail.com>: > As far as I remember, there is an optimization in Cassandra to manage > Paxos ballot per table. So asking a Paxos operation to span multiple tables > (even if same partition key) would require a lot of changes in the current > impl. > > The question has already been raised, you may want to convince the > committers by adding some comments here: https://issues.apache. > org/jira/browse/CASSANDRA-10085 > > On Mon, Oct 24, 2016 at 9:58 AM, Mickael Delanoë <delanoe...@gmail.com> > wrote: > >> Hi, >> >> I would like to use lightweight transaction inside a batch but the >> request is rejected by cassandra, however I think this is a use case than >> could be handled without problem. >> Below is what I wanted to do. >> >> I am using cassandra 3.7. >> >> CREATE KEYSPACE test_ksp WITH replication = {'class': 'SimpleStrategy', >> 'replication_factor': '1'}; >> >> CREATE TABLE test_ksp.item ( >> user_id bigint, >> item_id text, >> item_value text, >> item_key1 text, >> item_key2 text, >> PRIMARY KEY ((user_id), item_id)); >> >> CREATE TABLE test_ksp.item_id_by_key ( >> user_id bigint, >> item_key text, >> item_id text, >> PRIMARY KEY ((user_id), item_key)); >> >> USE test_ksp; >> >> BEGIN BATCH >> INSERT INTO item (user_id, item_id, item_value, item_key1, item_key2) >> values (1,'i11','item-C', 'key-XYZ-123', 'key-ABC-789') IF NOT EXISTS; >> INSERT INTO item_id_by_key (user_id, item_key, item_id) VALUES (1, >> 'key-XYZ-123', 'i11'); >> INSERT INTO item_id_by_key (user_id, item_key, item_id) VALUES (1, >> 'key-ABC-789', 'i11'); >> APPLY BATCH; >> >> >> So as you can see this is a batch that targets 2 tables but with the same >> partition key (i.e the same target nodes). Moreover It uses only ONE >> condition on one table only. >> I don't understand why cassandra returns an error "Batch with conditions >> cannot span multiple tables" in that case. >> >> I understand that if I had used several conditions on different tables it >> could be a problem, but in my case there is only one condition and moreover >> I have always the same partition key for every table inside the batch. >> As there is only one condition, I expected the paxos protocol just act on >> this condition and as the partition keys are all the same, the paxos >> protocol has only to work with the same replica nodes (not span across >> multiple partition). >> In my point of view this is as if the LWT was in a single statement, >> except that after the LWT is accepted a complete batch has to be executed. >> >> Is there someone that could explain why this use case need to be rejected >> by cassandra? And do you think this is something that cassandra could >> handle in a future version ? >> >> Regards, >> Mickaël >> >> > -- Mickaël Delanoë
