When executing following CQL commands:
The output is different between 2.x and 3.x:
2.x would although return same result if executed on a partition that does not exist at all:
It might be related to static column LWTs, as I could not reproduce same behaviour with non-static column LWTs. The most recent change was
CASSANDRA-10532, which enabled LWT operations on static columns with partition keys only. Another possible relation is (striked through since same happens on pre- CASSANDRA-9842, which removed distinction between null column and non-existing row. CASSANDRA-9842 code.