drop table if exists pt, c1, c2;

create table pt (id int primary key);

create table c1 (id int primary key, ref int references pt
deferrable initially deferred);

create table c2 (id int primary key, ref int references pt
deferrable initially deferred);

insert into pt values(11);
insert into c1 values(1, 11);
insert into c2 values(2, 11);

update pt set id = 12 where id = 11;  -- fails

with u1 as (
  update c1 set ref = 12 where ref = 11
)
update pt set id = 12 where id = 11;  -- fails

with u1 as (
  update c1 set ref = 12 where ref = 11
), u2 as (
  update c2 set ref = 12 where ref = 11
)
update pt set id = 12 where id = 11;  -- ok