postgres order of columns matters

gistfile1.sql

CREATE TABLE small (
    a smallint,
    b smallint,
    c integer,
    d integer,
    e date
)

CREATE TABLE big (
    c integer,
    a smallint,
    e date,
    b smallint,
    d integer
)


INSERT INTO small (a,b,c,d,e) 
SELECT i%32000, i%15000, i+1000,i+3000,current_date + i
FROM generate_series(1,1E6::integer) i

INSERT INTO big (a,b,c,d,e) 
SELECT i%32000, i%15000, i+1000,i+3000,current_date + i
FROM generate_series(1,1E6::integer) i

SELECT pg_size_pretty(pg_total_relation_size('small'));
 pg_size_pretty
----------------
 42 MB
(1 row)

SELECT pg_size_pretty(pg_total_relation_size('big'));
 pg_size_pretty
----------------
 50 MB
(1 row)

https://wiki.postgresql.org/wiki/Alter_column_position