BEGIN;
                                            BEGIN;

UPDATE b SET id = 10 WHERE id = 9;
                                            UPDATE b SET id = 9 WHERE id = 10; -- no row found
                                            LOCK b IN EXCLUSIVE MODE; -- will wait
LOCK b IN EXCLUSIVE MODE;
-- deadlock!

for i in {1..100}; do psql postgres post -c "select new_host2(109,'blah')"; done;

with w as ( insert into customer ...),
     w2 as (insert into collection ...)
select .. from customer ;

create or replace function f_test(v text) returns integer language sql security definer  as $$
  lock test in exclusive mode;
  with w as (insert into test(val) select v where not exists(select * from test where val=v)
             returning id)
  select id from test where val = v;
$$;

create or replace function f_test(v text) returns integer language sql security definer  as $$
  lock test in exclusive mode;
  with w  as (select ins.val, test.id from (values (v)) as ins(val) left join test using (val)),
       w2 as (insert into test(val) select val from w where w.id is null
              returning val, id)
  select coalesce(w2.id, w.id) as id from w left join w2 using (val);
$$;