[Django] #30032: Can't alter the default of a DateTimeField to be TransactionNow

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Dec 11, 2018, 1:05:50 PM12/11/18

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#30032: Can't alter the default of a DateTimeField to be TransactionNow
-------------------------------------+-------------------------------------
Reporter: Gavin | Owner: nobody
Wahl |
Type: Bug | Status: new
Component: Database | Version: 2.1
layer (models, ORM) |
Severity: Normal | Keywords:
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-------------------------------------+-------------------------------------
I have this field:
{{{
foo = models.DateTimeField(default=timezone.now)
}}}
I would like to modify it to use TransactionNow instead:
{{{
foo = models.DateTimeField(default=TransactionNow())
}}}
This migration operation is generated:
{{{
migrations.AlterField(
model_name='somemodel',
name='foo',
field=models.DateTimeField(default=django.contrib.postgres.functions.TransactionNow()),
),
}}}

When run, this error is thrown:

{{{
File "./manage.py", line 29, in <module>
execute_from_command_line(sys.argv)
File "django/core/management/__init__.py", line 381, in
execute_from_command_line
utility.execute()
File "django/core/management/__init__.py", line 375, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "django/core/management/base.py", line 316, in run_from_argv
self.execute(*args, **cmd_options)
File "django/core/management/base.py", line 353, in execute
output = self.handle(*args, **options)
File "django/core/management/base.py", line 83, in wrapped
res = handle_func(*args, **kwargs)
File "django/core/management/commands/migrate.py", line 203, in handle
fake_initial=fake_initial,
File "django/db/migrations/executor.py", line 117, in migrate
state = self._migrate_all_forwards(state, plan, full_plan, fake=fake,
fake_initial=fake_initial)
File "django/db/migrations/executor.py", line 147, in
_migrate_all_forwards
state = self.apply_migration(state, migration, fake=fake,
fake_initial=fake_initial)
File "django/db/migrations/executor.py", line 244, in apply_migration
state = migration.apply(state, schema_editor)
File "django/db/migrations/migration.py", line 124, in apply
operation.database_forwards(self.app_label, schema_editor, old_state,
project_state)
File "django/db/migrations/operations/fields.py", line 216, in
database_forwards
schema_editor.alter_field(from_model, from_field, to_field)
File "django/db/backends/base/schema.py", line 523, in alter_field
old_db_params, new_db_params, strict)
File "django/db/backends/postgresql/schema.py", line 122, in
_alter_field
new_db_params, strict,
File "django/db/backends/base/schema.py", line 626, in _alter_field
old_default = self.effective_default(old_field)
File "django/db/backends/base/schema.py", line 239, in effective_default
return field.get_db_prep_save(default, self.connection)
File "django/db/models/fields/__init__.py", line 790, in
get_db_prep_save
return self.get_db_prep_value(value, connection=connection,
prepared=False)
File "django/db/models/fields/__init__.py", line 1429, in
get_db_prep_value
value = self.get_prep_value(value)
File "django/db/models/fields/__init__.py", line 1408, in get_prep_value
value = super().get_prep_value(value)
File "django/db/models/fields/__init__.py", line 1268, in get_prep_value
return self.to_python(value)
File "django/db/models/fields/__init__.py", line 1369, in to_python
parsed = parse_datetime(value)
File "django/utils/dateparse.py", line 106, in parse_datetime
match = datetime_re.match(value)
TypeError: expected string or bytes-like object
}}}

If I create the field foo from scratch, with an AddField operation instead
of AlterField, it works as expected.

I should be able to modify a field to use TransactionNow() as a default.

--
Ticket URL: <https://code.djangoproject.com/ticket/30032>
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Django

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Dec 11, 2018, 1:48:11 PM12/11/18

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#30032: Can't alter the default of a DateTimeField to be TransactionNow
-------------------------------------+-------------------------------------

Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by Simon Charette):

* status: new => closed
* resolution: => duplicate

Comment:

Datebase level defaults are not supported yet, see #470.

--
Ticket URL: <https://code.djangoproject.com/ticket/30032#comment:1>

Django

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Dec 11, 2018, 3:25:58 PM12/11/18

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#30032: Can't alter the default of a DateTimeField to be TransactionNow
-------------------------------------+-------------------------------------

Has patch: 0 | Needs documentation: 0

Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Comment (by Gavin Wahl):

This isn't a database level default, that ticket is to support defaults
assigned by DDL. This is to support expressions as defaults.

--
Ticket URL: <https://code.djangoproject.com/ticket/30032#comment:2>

Django

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Dec 11, 2018, 4:49:02 PM12/11/18

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#30032: Allow expressions to be used for default

-------------------------------------+-------------------------------------
Reporter: Gavin Wahl | Owner: nobody

Type: New feature | Status: new
Component: Database layer | Version: master

(models, ORM) |
Severity: Normal | Resolution:

Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0

Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by Simon Charette):

* status: closed => new
* type: Bug => New feature
* version: 2.1 => master
* resolution: duplicate =>
* stage: Unreviewed => Accepted

Comment:

Sorry about the misinterpretation, #27222 seems related and I'm pretty
sure there's another ticket related to allowing `Now()` to be used for
`default` but I can't find it.

Tentatively accepting as a new feature request but as I said I'm pretty
sure there is already another ticket tracking this.

--
Ticket URL: <https://code.djangoproject.com/ticket/30032#comment:3>

Django

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Dec 20, 2018, 10:45:08 PM12/20/18

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#30032: Allow expressions to be used for default
-------------------------------------+-------------------------------------
Reporter: Gavin Wahl | Owner: nobody
Type: New feature | Status: new
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted

Has patch: 0 | Needs documentation: 0

Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Comment (by Tim Graham):

Simon, you might be thinking of this
[https://github.com/django/django/pull/9983 PR] which adds unofficial
support for something like `models.DateTimeField(default=Now)` on
PostgreSQL.

--
Ticket URL: <https://code.djangoproject.com/ticket/30032#comment:4>

Django

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Dec 21, 2018, 10:27:46 AM12/21/18

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#30032: Allow expressions to be used for default
-------------------------------------+-------------------------------------
Reporter: Gavin Wahl | Owner: nobody
Type: New feature | Status: new
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted

Has patch: 0 | Needs documentation: 0

Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Comment (by Simon Charette):

Thanks Tim, that's exactly what I had in mind. Should we close this ticket
in favour of #29444 then?

--
Ticket URL: <https://code.djangoproject.com/ticket/30032#comment:5>

Django

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Dec 21, 2018, 1:01:47 PM12/21/18

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#30032: Allow expressions to be used for default
-------------------------------------+-------------------------------------
Reporter: Gavin Wahl | Owner: nobody
Type: New feature | Status: new
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted

Has patch: 0 | Needs documentation: 0

Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Comment (by Tim Graham):

I think we should keep this open as there will be more work to do even if
that ticket is closed (adding support for other databases and making the
support official with documentation).

--
Ticket URL: <https://code.djangoproject.com/ticket/30032#comment:6>

Django

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Dec 21, 2018, 1:22:20 PM12/21/18

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#30032: Allow expressions to be used for default
-------------------------------------+-------------------------------------
Reporter: Gavin Wahl | Owner: nobody
Type: New feature | Status: new
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted

Has patch: 0 | Needs documentation: 0

Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Comment (by Simon Charette):

Makes sense, thanks for chiming in.

--
Ticket URL: <https://code.djangoproject.com/ticket/30032#comment:7>

Django

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Nov 21, 2019, 11:18:10 AM11/21/19

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#30032: Allow expressions to be used for default
-------------------------------------+-------------------------------------

Reporter: Gavin Wahl | Owner: Johannes
| Hoppe
Type: New feature | Status: assigned

Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted

Has patch: 1 | Needs documentation: 0

Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by Johannes Hoppe):

* cc: Johannes Hoppe (added)
* owner: nobody => Johannes Hoppe
* has_patch: 0 => 1
* status: new => assigned

--
Ticket URL: <https://code.djangoproject.com/ticket/30032#comment:8>

Django

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Dec 11, 2019, 7:21:16 AM12/11/19

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Has patch: 1 | Needs documentation: 1
Needs tests: 1 | Patch needs improvement: 0

Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by felixxm):

* needs_docs: 0 => 1
* needs_tests: 0 => 1

Comment:

Simon left comments.

--
Ticket URL: <https://code.djangoproject.com/ticket/30032#comment:9>

Django

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Jan 31, 2020, 5:09:37 AM1/31/20

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Has patch: 1 | Needs documentation: 0

Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by Johannes Hoppe):

* needs_docs: 1 => 0
* needs_tests: 1 => 0

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Ticket URL: <https://code.djangoproject.com/ticket/30032#comment:10>

Django

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Feb 1, 2020, 1:42:13 PM2/1/20

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Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 1

Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by Johannes Hoppe):

* needs_better_patch: 0 => 1

--
Ticket URL: <https://code.djangoproject.com/ticket/30032#comment:11>

Django

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Feb 1, 2020, 5:56:03 PM2/1/20

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Has patch: 1 | Needs documentation: 0

Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by Johannes Hoppe):

* needs_better_patch: 1 => 0

--
Ticket URL: <https://code.djangoproject.com/ticket/30032#comment:12>

Django

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Jul 21, 2020, 6:15:22 AM7/21/20

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Has patch: 1 | Needs documentation: 0
Needs tests: 1 | Patch needs improvement: 1

Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by felixxm):

* needs_better_patch: 0 => 1

* needs_tests: 0 => 1

--
Ticket URL: <https://code.djangoproject.com/ticket/30032#comment:13>

Django

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Sep 1, 2020, 1:31:52 PM9/1/20

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Has patch: 1 | Needs documentation: 0

Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by Johannes Hoppe):

* needs_better_patch: 1 => 0

* needs_tests: 1 => 0

--
Ticket URL: <https://code.djangoproject.com/ticket/30032#comment:14>

Django

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Sep 3, 2020, 3:55:44 AM9/3/20

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Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 1

Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by Johannes Hoppe):

* needs_better_patch: 0 => 1

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Ticket URL: <https://code.djangoproject.com/ticket/30032#comment:15>

Django

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Sep 4, 2020, 5:25:21 AM9/4/20

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Has patch: 1 | Needs documentation: 0

Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by Johannes Hoppe):

* needs_better_patch: 1 => 0

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Ticket URL: <https://code.djangoproject.com/ticket/30032#comment:16>

Django

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Oct 23, 2020, 8:04:37 PM10/23/20

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Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 1

Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by InvalidInterrupt):

* needs_better_patch: 0 => 1

--
Ticket URL: <https://code.djangoproject.com/ticket/30032#comment:17>

Django

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Nov 14, 2020, 12:56:02 PM11/14/20

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#30032: Allow expressions to be used for default
-------------------------------------+-------------------------------------
Reporter: Gavin Wahl | Owner: Johannes

| Maron

Has patch: 1 | Needs documentation: 0

Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by Johannes Maron):

* needs_better_patch: 1 => 0

--
Ticket URL: <https://code.djangoproject.com/ticket/30032#comment:18>

Django

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Dec 18, 2020, 4:29:08 AM12/18/20

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Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 1

Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by Mariusz Felisiak):

* needs_better_patch: 0 => 1

Comment:

Marking as "needs improvement" per Simon's comments.

--
Ticket URL: <https://code.djangoproject.com/ticket/30032#comment:19>

Django

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Feb 21, 2021, 5:54:15 AM2/21/21

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Has patch: 1 | Needs documentation: 0

Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by Johannes Maron):

* needs_better_patch: 1 => 0

--
Ticket URL: <https://code.djangoproject.com/ticket/30032#comment:20>

Django

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Mar 5, 2022, 6:22:14 AM3/5/22

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#30032: Allow expressions to be used for default
-------------------------------------+-------------------------------------
Reporter: Gavin Wahl | Owner: Johannes
| Maron
Type: New feature | Status: assigned

Component: Database layer | Version: dev

(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted

Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 1

Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by Mariusz Felisiak):

* needs_better_patch: 0 => 1

--
Ticket URL: <https://code.djangoproject.com/ticket/30032#comment:21>

Django

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Jun 23, 2022, 4:30:34 AM6/23/22

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Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 1

Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by Brian Helba):

* cc: Brian Helba (added)

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Ticket URL: <https://code.djangoproject.com/ticket/30032#comment:22>

Django

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Oct 30, 2023, 3:22:21 PM10/30/23

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Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 1

Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Comment (by Natalia Bidart):

Refreshed [https://github.com/django/django/pull/11783/ the PR] with a
rebase and conflict/style fixes, but it still needs work fixing failing
tests.

--
Ticket URL: <https://code.djangoproject.com/ticket/30032#comment:23>

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