PG 浮点数精度显示问题

• 使用默认精度

create table test(id double precision);

insert into test values (1.1234567890123456789);
insert into test values (1.1234567890012345678);
insert into test values (1.1234567890012545678);
insert into test values (10.1234567890012545678);
insert into test values (123.012345678901234567);
select * from test;
        id
------------------
 1.12345678901235
 1.12345678900123
 1.12345678900125
 10.1234567890013
 123.012345678901
 1.12345678901235
 1.12345678900123
 1.12345678900125
 10.1234567890013
 123.012345678901
(10 rows)

• 修改默认精度

postgres=# show extra_float_digits ;
 extra_float_digits
--------------------
 1
(1 row)

postgres=# set extra_float_digits to 3;
SET
postgres=#

postgres=# show extra_float_digits ;
 extra_float_digits
--------------------
 3
(1 row)

postgres=# select id from test SF;
         id
---------------------
 1.12345678901234569
 1.12345678900123458
 1.12345678900125456
10.1234567890012546
 123.012345678901241
 1.12345678901234569
 1.12345678900123458
 1.12345678900125456
 10.1234567890012546
 123.012345678901241