Hi Sumatra,
Thanks for the FLIP. The ability to leverage RocksDB merge operators in
Reducing/Aggregating state is a really meaningful improvement.
I share similar concerns about the user interface with the previous comments:
• If new state types are introduced, can users migrate their existing jobs
from ReducingState to ReducingMergeState? Since the core logic of the
ReduceFunction remains the same, one would expect a straightforward migration
path. If yes, will checkpoints/savepoints remain compatible across this switch
(and back)?
• Will this introduce different semantics when State TTL is enabled?
