Timestamp fields in django

Question

I have a MySQL database, right now I\'m generating all of the datetime fields as models.DateTimeField. Is there a way to get a timestamp instead? I

Answer 1

There was actually a very good and informative article on this. Here: http://ianrolfe.livejournal.com/36017.html

The solution on the page is slightly deprecated, so I did the following:

from django.db import models
from datetime import datetime
from time import strftime

class UnixTimestampField(models.DateTimeField):
    """UnixTimestampField: creates a DateTimeField that is represented on the
    database as a TIMESTAMP field rather than the usual DATETIME field.
    """
    def __init__(self, null=False, blank=False, **kwargs):
        super(UnixTimestampField, self).__init__(**kwargs)
        # default for TIMESTAMP is NOT NULL unlike most fields, so we have to
        # cheat a little:
        self.blank, self.isnull = blank, null
        self.null = True # To prevent the framework from shoving in "not null".

    def db_type(self, connection):
        typ=['TIMESTAMP']
        # See above!
        if self.isnull:
            typ += ['NULL']
        if self.auto_created:
            typ += ['default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP']
        return ' '.join(typ)

    def to_python(self, value):
        if isinstance(value, int):
            return datetime.fromtimestamp(value)
        else:
            return models.DateTimeField.to_python(self, value)

    def get_db_prep_value(self, value, connection, prepared=False):
        if value==None:
            return None
        # Use '%Y%m%d%H%M%S' for MySQL < 4.1
        return strftime('%Y-%m-%d %H:%M:%S',value.timetuple())

To use it, all you have to do is: timestamp = UnixTimestampField(auto_created=True)

In MySQL, the column should appear as: 'timestamp' timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,

Only drawback with this is that it only works on MySQL databases. But you can easily modify it for others.

Answer 2

The pip package django-unixdatetimefield provides a UnixDateTimeField field that you can use for this out of the box (https://pypi.python.org/pypi/django-unixdatetimefield/).

Example model:

from django_unixdatetimefield import UnixDateTimeField

class MyModel(models.Model):
    created_at = UnixDateTimeField()

Python ORM query:

>>> m = MyModel()
>>> m.created_at = datetime.datetime(2015, 2, 21, 19, 38, 32, 209148)
>>> m.save()

Database:

sqlite> select created_at from mymodel;
1426967129

Here's the source code if interested - https://github.com/Niklas9/django-unixdatetimefield.

Disclaimer: I'm the author of this pip package.

Answer 3

To automatically update on insert and update use this:

created = DateTimeField(auto_now_add=True, editable=False, null=False, blank=False)
last_modified = DateTimeField(auto_now=True, editable=False, null=False, blank=False)

The DateTimeField should store UTC (check your DB settings, I know from Postgres that there it is the case). You can use l10n in the templates and format via:

{{ object.created|date:'SHORT_DATETIME_FORMAT' }}

Seconds since Unix Epoch:

{{ object.created|date:'U' }}

See https://docs.djangoproject.com/en/1.10/ref/templates/builtins/#date

Answer 4

django-extensions has a useful TimeStampedModel: https://django-extensions.readthedocs.io/en/latest/model_extensions.html