Postgres 11

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create table test_temporal (
  id SERIAL,
  name varchar(16)
);

create or replace view test as
SELECT * from test_temporal;

create or replace function test_temporal_insert()
returns trigger as $$
begin

INSERT INTO test_temporal ( id, name )
values ( coalesce( new.id, DEFAULT ), new.name );
return NEW;
end;
$$ language plpgsql;

create trigger test_temporal_insert
instead of insert on test
for each row execute procedure test_temporal_insert();


insert into test ( name ) values ( 'a' );
ERROR:  DEFAULT is not allowed in this context
LINE 2: values ( coalesce( new.id, DEFAULT ), new.name )
                                   ^
QUERY:  INSERT INTO test_temporal ( id, name )
values ( coalesce( new.id, DEFAULT ), new.name )
CONTEXT:  PL/pgSQL function test_temporal_insert() line 4 at SQL statement


select * from test;