Django with postgresql, the datetime microsecond's leading 0 is disappeared

Question

I'm trying to retrieve datetime typed data from postgresql on django.

But if the microsecond has leading 0, like below

|        datetime_field        |
|2021-06-07 09:22:13.099866+00 |

the result is shown as

datetime.datetime(2021, 6, 7, 9, 22, 13, 998660, tzinfo=<UTC>)

in Python.

Take notice of microsecond 099866. It has been changed to 998660.

If I insert the resulted datetime object without any change to postgresql, it is uploaded as below.

|        datetime_field        |
| 2021-06-07 09:22:13.99866+00 |

The 0 at the head is disappeared.

It seems this problem is derived from psycopg2, not just django but I can't find any resolution for this.

How can I get the microseconds in its entierty?

p.s. Welcome for editing for just the English. As I'm not an English speaker, I'm not sure whether I wrote correct expressions.

---

Addition of the exact step.

I'm doing the job on docker containers. Two containers are used now, each for django server and PostgreSQL server.

Version infos:
Python 3.9.1
Django==3.1.4
psycopg2==2.8.6
postgres (PostgreSQL) 13.1 (Debian 13.1-1.pgdg100+1)

I'm testing with a clone of production database.

1. SELECT query for a problematic data.

TEST=# SELECT issued_at FROM table_name WHERE id = 153;
           issued_at
-------------------------------
 2021-06-18 10:10:49.075392+00
(1 row)

2. In python manage.py shell, retrieve data with connections.cursor()

>>> with transaction.atomic():
...     query = f'''SELECT issued_at FROM table_name WHERE id = 153;'''
...     with connections['test_db'].cursor() as cursor: 
...             cursor.execute(query)
...             print(cursor.fetchone())
...
(datetime.datetime(2021, 6, 18, 10, 10, 49, 753920, tzinfo=<UTC>),)

---

Addition 2.

When I get data with django's Model.objects.get(), the result comes out good.

>>> data = TableName.objects.get(id=153)
>>> data.issued_at
datetime.datetime(2021, 6, 18, 10, 10, 49, 75392, tzinfo=<UTC>)

It seems a kind of problem of django.db.connections.

Answer 1

I'm not seeing it:

CREATE TABLE public.dt_test (
    id integer,
    ts_fld timestamp without time zone,
    tsz_fld timestamp with time zone
);
insert into dt_test values (1, '2021-06-07 09:22:13.099866+00', '2021-06-07 09:22:13.099866+00');
insert into dt_test values (2, '2021-06-07 09:22:13.99866+00', '2021-06-07 09:22:13.99866+00');
select * from dt_test ;
 id |           ts_fld           |            tsz_fld            
----+----------------------------+-------------------------------
  1 | 2021-06-07 09:22:13.099866 | 2021-06-07 02:22:13.099866-07
  2 | 2021-06-07 09:22:13.99866  | 2021-06-07 02:22:13.99866-07

import psycopg2 
cur.execute('select * from dt_test')
rs = cur.fetchall()
rs                                                                                                                                                                        
Out[23]: 
[(1,
  datetime.datetime(2021, 6, 7, 9, 22, 13, 99866),
  datetime.datetime(2021, 6, 7, 2, 22, 13, 99866, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=-420, name=None))),
 (2,
  datetime.datetime(2021, 6, 7, 9, 22, 13, 998660),
  datetime.datetime(2021, 6, 7, 2, 22, 13, 998660, tzinfo=psycopg2.tz.FixedOffsetTimezone(offset=-420, name=None)))]
cur.execute('insert into dt_test(id, ts_fld) values(%s, %s)', [3, datetime.datetime(2021, 6, 7, 9, 22, 13, 99866)])
con.commit()
 select * from dt_test ;
 id |           ts_fld           |            tsz_fld            
----+----------------------------+-------------------------------
  1 | 2021-06-07 09:22:13.099866 | 2021-06-07 02:22:13.099866-07
  2 | 2021-06-07 09:22:13.99866  | 2021-06-07 02:22:13.99866-07
  3 | 2021-06-07 09:22:13.099866 | NULL

What you are seeing is normalization to 1000000:

select 998660/1000000.0;
        ?column?        
------------------------
 0.99866000000000000000

select 99866/1000000.0;
        ?column?        
------------------------
 0.09986600000000000000