The issue could be with how comment updates are being handled. The problem arises because comment updates are executed through the ALTER TABLE command, which modifies table metadata. When multiple transactions attempt to update metadata at the same time—such as simultaneous comment updates and merge operations on the same column—concurrency conflicts can occur, leading to the observed exceptions. Since ALTER TABLE operations (including SET TBLPROPERTIES and CHANGE COLUMN) directly modify metadata, concurrent attempts to update these properties are especially prone to conflicts. To mitigate this, I suggest avoiding concurrent comment updates on the same column wherever possible and implementing retry logic if the issue is intermittent. Can you try this out? If this did not work out, please send the full error stack logs.