I’m a bit torn here, as consistency with counters is important. But they are a unique eventually consistent data type, and I am inclined to default standard numeric types to behave as SQL does, since they write a new value rather than a “delta”
It is far from optimal to have divergent behaviours, but also suboptimal to diverge from relational algebra, and probably special casing counters is the least bad outcome IMO. > On 30 Aug 2022, at 22:52, David Capwell <dcapw...@gmail.com> wrote: > > > 4.1 added the ability for LWT to support "UPDATE ... SET name = name + 42", > but we never really fleshed out with the larger community what the semantics > should be in the case where the column or row are NULL; I opened up > https://issues.apache.org/jira/browse/CASSANDRA-17857 for this issue. > > As I see it there are 3 possible outcomes: > 1) fail the query > 2) null + 42 = null (matches SQL) > 3) null + 42 == 0 + 42 = 42 (matches counters) > > In SQL you get NULL (option 2), but CQL counters treat NULL as 0 (option 3) > meaning we already do not match SQL (though counters are not a standard SQL > type so might not be applicable). Personally I lean towards option 3 as the > "zero" for addition and subtraction is 0 (1 for multiplication and division). > > So looking for feedback so we can update in CASSANDRA-17857 before 4.1 > release. > >
