P.S. I guess my suggestion could be treated as an optional follow-up improvement if you can reliably detect FIRST_RUN case vs RERUN, but we could also just do that so to not have to trust neither the index state nor the state of the StepContext.

Running a single delete query for the whole block would be efficient enough to allow us to run it always, just in case, so it's the more robust solution as we don't have to trust existing state and possible corruption issues.