Apologies for the necromancer here but just chiming in that I also got bitten by this in our production systems today. It’s precisely the same pattern - MERGEing into a “part” of a table. Would be nice if MERGE allowed you to specify a “filter” or something so it only affected a subsection of the table - but Toms suggestion of pushing down the condition would also have saved me. For now I’m just going to have to abandon the MERGE construct and go back to separate INSERT and DELETE’s.
