Acquire a transaction-scoped advisory lock for the given composite trigger.This serializes concurrent child trigger evaluations for the same compound
trigger, preventing a race condition where multiple transactions each see
only their own child firing and neither fires the parent.The lock is automatically released when the transaction commits or rolls back.
Delete the specified child firings and return the IDs that were actually deleted.Returns the set of child_firing_ids that were successfully deleted. Callers can
compare this to the expected firing_ids to detect races and avoid double-firing
composite triggers.
