The following document <https://docs.google.com/document/d/1A6zFkjxnC_-9RwG4h0sI81KI5ZEvJ7HzgClCUFpB5WE/edit?ts=5a793606#> describes a proposal for enforcing batch sizing constraints (count and memory) within the Parquet Reader (Flat Schema). Please feel free to take a look and provide feedback.
Thanks! Regards, Salim