So far postgres' statement level triggers do not have access to changed rows so far, be it an INSTEAD OF or any other kind of trigger. There has been some noise

So far postgres' statement level triggers do not have access to changed rows so far, be it an INSTEAD OF or any other kind of trigger. There has been some noise towards supporting it for AFTER triggers - I doubt we'll see BEFORE support, it's unclear to me what that'd even mean.