Hi Amir, For the current Flink, you have to iterator the returned Iterable of ListState#get().
Why Flink lacks an API to get the size of listState directly? This is because Flink leverages RocksDB's merge operator [1] for high-performance listState#add [2], that is to say, we would not even read the original data when appending the listState. I think you can record the size in another valueState when implementing your logic. [1] https://github.com/facebook/rocksdb/wiki/Merge-Operator [2] https://github.com/apache/flink/blob/d8c64a808484cab78c8bd7b74a287edf7d1f3b01/flink-state-backends/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDBListState.java#L131 Best Yun Tang ________________________________ From: Amir Hossein Sharifzadeh <amirsharifza...@gmail.com> Sent: Tuesday, May 23, 2023 23:51 To: dev <dev@flink.apache.org> Subject: How to figure out what's the size of ListState? Dear Flink Dev team, It's about a while since I am dealing with an issue that can't figure out myself. I spent quite a lot of time trying to solve the problem myself, but I feel stuck. I explained the problem statement and the issue here: https://stackoverflow.com/questions/76308686/how-to-figure-out-whats-the-size-of-liststate I really appreciate any suggestion. Best, Amir
