The previous comment claimed each UPDATE couldn't hold any bucket lock
that would deadlock with the trigger path, which conflated statement-
level locks with TX-level locks. By the time we reach this loop the TX
already holds bucket-row X-locks from the earlier DELETEs plus any ES
X-locks acquired by the bucket DELETE triggers cascading. Rewrite the
comment to distinguish those TX-held locks from the locks acquired by
the new UPDATE statement and to be explicit that the TX's lock
acquisition direction is preserved.
52d5f80e08