PG not-null constraint as a check

not_null_check

[development] # CREATE TABLE test (id integer, name text);
[development] # ALTER TABLE test ADD CHECK (name is not null) NOT VALID;
[development] # \d test
     Table "public.test"
 Column |  Type   | Modifiers
--------+---------+-----------
 id     | integer |
 name   | text    |
Check constraints:
    "test_name_check" CHECK (name IS NOT NULL) NOT VALID

[development] # ALTER TABLE test VALIDATE CONSTRAINT "test_name_check";
[development] # INSERT INTO test VALUES (1, NULL);
ERROR:  23514: new row for relation "test" violates check constraint "test_name_check"
DETAIL:  Failing row contains (1, null).