#28715: Migration DateTimeField(auto_now_add=True ->
default=django.utils.timezone.new)
------------------------------------------+------------------------
Reporter: Дилян Палаузов | Owner: nobody
Type: Uncategorized | Status: new
Component: Migrations | Version: 1.11
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
------------------------------------------+------------------------
A switch from DateTimeField(auto_now_add=True) to
DateTimeField(default=django.utils.timezone.new) creates the statements
ALTER TABLE SET DEFAULT '2017-10-16T09:35:52.710695'::timestamp;
ALTER TABLE DROP DEFAULT
which have no effects, apart from locking the whole table.
A proposal to recognize, when the effective default-callable doesn't
change:
{{{
diff --git a/django/db/backends/base/schema.py
b/django/db/backends/base/schema.py
--- a/django/db/backends/base/schema.py
+++ b/django/db/backends/base/schema.py
@@ -199,28 +199,32 @@ class BaseDatabaseSchemaEditor(object):
'requires_literal_defaults must provide a prepare_default()
method'
)
- def effective_default(self, field):
+ def effective_default_before_callable(self, field):
"""
- Returns a field's effective database default value
+ Returns a field's effective database default callable or value
"""
if field.has_default():
- default = field.get_default()
+ return field._get_default
elif not field.null and field.blank and
field.empty_strings_allowed:
if field.get_internal_type() == "BinaryField":
- default = six.binary_type()
+ return six.binary_type()
else:
- default = six.text_type()
+ return six.text_type()
elif getattr(field, 'auto_now', False) or getattr(field,
'auto_now_add', False):
default = datetime.now()
internal_type = field.get_internal_type()
if internal_type == 'DateField':
- default = default.date
+ return default.date
elif internal_type == 'TimeField':
- default = default.time
+ return default.time
elif internal_type == 'DateTimeField':
- default = timezone.now
- else:
- default = None
+ return timezone.now
+
+ def effective_default(self, field):
+ """
+ Returns a field's effective database default value
+ """
+ default = self.effective_default_before_callable(field)
# If it's a callable, call it
if callable(default):
default = default()
@@ -615,6 +619,7 @@ class BaseDatabaseSchemaEditor(object):
old_default != new_default and
new_default is not None and
not self.skip_default(new_field)
+ and self.effective_default_before_callable(old_field) !=
self.effective_default_before_callable(new
)
if needs_database_default:
if self.connection.features.requires_literal_defaults:
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/28715>
Django <https://code.djangoproject.com/>
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