What do you mean by Batch Statements are atomic in cassandra? Docs are a bit confusing in nature to be precise. Does it mean that queries are atomic across nodes in cluster?

Say,for example, i have a batch with 100 queries. If the 40th query in batch fails, what happens to the 39 queries executed in the batch?

I understand that there is a batchlog created under the hood and it will take care of the consistency for partial batches. Does it remove the rest of the 39 entries and provide the required atomic nature of batch queries. 

In MYSQL, we set autocommit to false and hence we can rollback. Does cassandra rollback in those cases?