After a lengthy discussion on the dev list, the community seems to have arrived at the following list of TODOs before we release SAI in 5.0:
1.) CREATE INDEX should be expanded to support USING … WITH OPTIONS…
Essentially, we should be able to do something like CREATE INDEX ON tbl(v) USING ’sai’ WITH OPTIONS = ... and CREATE INDEX ON tbl(v) USING ‘cassandra’ as a more specific/complete way to emulate the current behavior of CREATE INDEX.
2.) Allow operators to configure, in the YAML, a.) whether an index implementation must be specified w/ USING and CREATE INDEX and b.) what the default implementation will be, if USING isn’t required.
3.) The defaults we ship w/ will avoid breaking existing CREATE INDEX usage. (i.e. A default is allowed, and that default will remain ‘cassandra’, or the legacy 2i)
With all this in place, users should be able create SAI indexes w/ the simplest possible syntax, no defaults will change, and operators will have the ability to change defaults to favor SAI whenever they like.