Dmytro Shkvyra, Note that interface RelOptPlanner.Executor still exists. It extends the new interface RexExecutor, so if your class implements Executor if will now also implement RexExecutor, with no code changes or re-compile. interface RelOptPlanner.Executor is deprecated, but you can continue to use it until calcite-2.0, or upgrade to RexExecutor when convenient.
We have tried to be consistent with the principles of semantic versioning. If we have broken binary compatibility and there is something we can do to fix it, let us know. And I think the fix I have already made is an improvement, at least.