the docs also say "every statement is atomic" and the ambiguity around whether merge is one statement or two (or three) ought to be settled by explicitly stating our atomicity expectations with a transaction. anyway my experience has been that adding the lock hints "fixes" the problem with pk violations during concurrent upserts and it seemed to be commonly known and widely used afaict. fwiw I agree with not adopting "merge w/hints" as the syntax for upsert I just thought the decision had more to do with the aversion to hints but I stand corrected (also from reading some of the links here I see that even merge w/hints has a potential deadlock if you get unlucky with the range locks it uses under the hood - I never hit that in practice myself, but it seems clear that sql should have a standard more constrained upsert so that further supports your original decision)