Unexpected unnamed sink in SQL job

[Paul Lam]

Hi, 

I noticed that a simple SQL like 'insert into hive_parquet_table select … from 
some_kafka_table' will generates an additional operator called ’Sink: Unnamed’ 
with parallelism 1. I wonder if it’s by design? And what’s the functionality of 
this operator?

Thanks in advance!

Env: 
- Flink 1.11.0 with Blink planner 
- Hive 1.1.0

Best,
Paul Lam