RisingWave Community - Is there a way to buffer up messages from a source before sending to a sink in Kafka?

Neil is trying to buffer up messages from a source before sending them to a sink in Kafka.
He attempted to use WATERMARK but it did not produce the expected outcome.
Neil's specific use case involves sinking data to Iceberg and wanting to optimize the table in between batches.
The current issue seems to be related to commit conflicts in the Iceberg table, which may be caused by the coupling of commits with checkpoints.
To reduce the chance of commit conflicts, increasing the checkpoint interval, such as setting checkpoint_frequency to a larger value, is recommended.
There is ongoing work to decouple commits from checkpoints in the system.