SELECT
 '(1,2)'::point 
 ,point '(2.0,0)'
 ,(1.2,2.1)/*record, not point*/
 ,(point '(2.0,0)')[0]
/*, array[1.1,2.1]::point --ОШИБКА:  преобразовать тип numeric[] в point нельзя */
;

create table test2
(a serial primary key
,b serial
);
ALTER TABLE test2 ALTER COLUMN b DROP NOT NULL;
INSERT INTO test2 (b) VALUES
	( 1)
	,(2)
	,(3)
	,(DEFAULT )
	,(DEFAULT )
	,(DEFAULT )
	;
SELECT * FROM test2;
/*----------------
1;1
2;2
3;3
4;1
5;2
6;3
----------------*/
DROP TABLE test2;

SELECT
--'(NULL,0.5)'::point
(NULL::point ~= NULL::point) IS NULL
-- ОК
-- bug 1:
,'(Infinity,0.5)'::point ~='(Infinity,0.5)'::point
, 'Infinity'::double precision = 'Infinity'::double precision 

-- bug 2:
,'(-Infinity,0.5)'::point ~='(-Infinity,0.5)'::point
, -'Infinity'::double precision = -'Infinity'::double precision 

-- bug 3:
,'(NaN,0.5)'::point ~='(NaN,0.5)'::point
,'NaN'::double precision = -'NaN'::double precision
,'NaN'::double precision = 'NaN'::double precision