Hey everyone! I'll keep this short. SASI and later SAI, in lieu of anything resembling a query planner, have always just greedily returned a min long from Index#getEstimatedResultRows(), thereby stealing the right to be used to execute the query even when a legacy 2i is present on the relevant columns. If we have a user that needs to migrate away from a legacy 2i, this seems like the exact opposite of what we want to do by default. I want to propose that we invert this behavior, and have legacy 2i continue to serve queries instead of new SAI indexes by default until they are dropped.
Note that we'll have more options around this when CASSANDRA-18112 <https://issues.apache.org/jira/browse/CASSANDRA-18112> lands, but for now the change in default seems valuable. Thoughts?
