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Fixed #470 -- Added support for database defaults on fields. 

Special thanks to Hannes Ljungberg for finding multiple implementation
gaps.

Thanks also to Simon Charette, Adam Johnson, and Mariusz Felisiak for
reviews.
This commit is contained in:
Ian Foote 2020-11-22 22:27:57 +00:00 committed by Mariusz Felisiak
parent 599f3e2cda
commit 7414704e88
32 changed files with 1089 additions and 34 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
AUTHORS
View File

@ -587,6 +587,7 @@ answer newbie questions, and generally made Django that much better:
lerouxb@gmail.com
Lex Berezhny <lex@damoti.com>
Liang Feng <hutuworm@gmail.com>
Lily Foote
limodou
Lincoln Smith <lincoln.smith@anu.edu.au>
Liu Yijie <007gzs@gmail.com>

12
django/db/backends/base/features.py
View File

@ -201,6 +201,15 @@ class BaseDatabaseFeatures:
# Does the backend require literal defaults, rather than parameterized ones?
requires_literal_defaults = False
# Does the backend support functions in defaults?
supports_expression_defaults = True
# Does the backend support the DEFAULT keyword in insert queries?
supports_default_keyword_in_insert = True
# Does the backend support the DEFAULT keyword in bulk insert queries?
supports_default_keyword_in_bulk_insert = True
# Does the backend require a connection reset after each material schema change?
connection_persists_old_columns = False
@ -361,6 +370,9 @@ class BaseDatabaseFeatures:
# SQL template override for tests.aggregation.tests.NowUTC
test_now_utc_template = None
# SQL to create a model instance using the database defaults.
insert_test_table_with_defaults = None
# A set of dotted paths to tests in Django's test suite that are expected
# to fail on this database.
django_test_expected_failures = set()

88
django/db/backends/base/schema.py
View File

@ -12,7 +12,7 @@ from django.db.backends.ddl_references import (
Table,
)
from django.db.backends.utils import names_digest, split_identifier, truncate_name
from django.db.models import Deferrable, Index
from django.db.models import NOT_PROVIDED, Deferrable, Index
from django.db.models.sql import Query
from django.db.transaction import TransactionManagementError, atomic
from django.utils import timezone
@ -296,6 +296,12 @@ class BaseDatabaseSchemaEditor:
yield self._comment_sql(field.db_comment)
# Work out nullability.
null = field.null
# Add database default.
if field.db_default is not NOT_PROVIDED:
default_sql, default_params = self.db_default_sql(field)
yield f"DEFAULT {default_sql}"
params.extend(default_params)
include_default = False
# Include a default value, if requested.
include_default = (
include_default
@ -400,6 +406,22 @@ class BaseDatabaseSchemaEditor:
"""
return "%s"
def db_default_sql(self, field):
"""Return the sql and params for the field's database default."""
from django.db.models.expressions import Value
sql = "%s" if isinstance(field.db_default, Value) else "(%s)"
query = Query(model=field.model)
compiler = query.get_compiler(connection=self.connection)
default_sql, params = compiler.compile(field.db_default)
if self.connection.features.requires_literal_defaults:
# Some databases doesn't support parameterized defaults (Oracle,
# SQLite). If this is the case, the individual schema backend
# should implement prepare_default().
default_sql %= tuple(self.prepare_default(p) for p in params)
params = []
return sql % default_sql, params
@staticmethod
def _effective_default(field):
# This method allows testing its logic without a connection.
@ -1025,6 +1047,21 @@ class BaseDatabaseSchemaEditor:
)
actions.append(fragment)
post_actions.extend(other_actions)
if new_field.db_default is not NOT_PROVIDED:
if (
old_field.db_default is NOT_PROVIDED
or new_field.db_default != old_field.db_default
):
actions.append(
self._alter_column_database_default_sql(model, old_field, new_field)
)
elif old_field.db_default is not NOT_PROVIDED:
actions.append(
self._alter_column_database_default_sql(
model, old_field, new_field, drop=True
)
)
# When changing a column NULL constraint to NOT NULL with a given
# default value, we need to perform 4 steps:
# 1. Add a default for new incoming writes
@ -1033,7 +1070,11 @@ class BaseDatabaseSchemaEditor:
# 4. Drop the default again.
# Default change?
needs_database_default = False
if old_field.null and not new_field.null:
if (
old_field.null
and not new_field.null
and new_field.db_default is NOT_PROVIDED
):
old_default = self.effective_default(old_field)
new_default = self.effective_default(new_field)
if (
@ -1051,9 +1092,9 @@ class BaseDatabaseSchemaEditor:
if fragment:
null_actions.append(fragment)
# Only if we have a default and there is a change from NULL to NOT NULL
four_way_default_alteration = new_field.has_default() and (
old_field.null and not new_field.null
)
four_way_default_alteration = (
new_field.has_default() or new_field.db_default is not NOT_PROVIDED
) and (old_field.null and not new_field.null)
if actions or null_actions:
if not four_way_default_alteration:
# If we don't have to do a 4-way default alteration we can
@ -1074,15 +1115,20 @@ class BaseDatabaseSchemaEditor:
params,
)
if four_way_default_alteration:
if new_field.db_default is NOT_PROVIDED:
default_sql = "%s"
params = [new_default]
else:
default_sql, params = self.db_default_sql(new_field)
# Update existing rows with default value
self.execute(
self.sql_update_with_default
% {
"table": self.quote_name(model._meta.db_table),
"column": self.quote_name(new_field.column),
"default": "%s",
"default": default_sql,
},
[new_default],
params,
)
# Since we didn't run a NOT NULL change before we need to do it
# now
@ -1264,6 +1310,34 @@ class BaseDatabaseSchemaEditor:
params,
)
def _alter_column_database_default_sql(
self, model, old_field, new_field, drop=False
):
"""
Hook to specialize column database default alteration.
Return a (sql, params) fragment to add or drop (depending on the drop
argument) a default to new_field's column.
"""
if drop:
sql = self.sql_alter_column_no_default
default_sql = ""
params = []
else:
sql = self.sql_alter_column_default
default_sql, params = self.db_default_sql(new_field)
new_db_params = new_field.db_parameters(connection=self.connection)
return (
sql
% {
"column": self.quote_name(new_field.column),
"type": new_db_params["type"],
"default": default_sql,
},
params,
)
def _alter_column_type_sql(
self, model, old_field, new_field, new_type, old_collation, new_collation
):

7
django/db/backends/mysql/features.py
View File

@ -51,6 +51,7 @@ class DatabaseFeatures(BaseDatabaseFeatures):
# COLLATE must be wrapped in parentheses because MySQL treats COLLATE as an
# indexed expression.
collate_as_index_expression = True
insert_test_table_with_defaults = "INSERT INTO {} () VALUES ()"
supports_order_by_nulls_modifier = False
order_by_nulls_first = True
@ -342,3 +343,9 @@ class DatabaseFeatures(BaseDatabaseFeatures):
if self.connection.mysql_is_mariadb:
return self.connection.mysql_version >= (10, 5, 2)
return True
@cached_property
def supports_expression_defaults(self):
if self.connection.mysql_is_mariadb:
return True
return self.connection.mysql_version >= (8, 0, 13)

29
django/db/backends/mysql/schema.py
View File

@ -209,11 +209,15 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
self._create_missing_fk_index(model, fields=fields)
return super()._delete_composed_index(model, fields, *args)
def _set_field_new_type_null_status(self, field, new_type):
def _set_field_new_type(self, field, new_type):
"""
Keep the null property of the old field. If it has changed, it will be
handled separately.
Keep the NULL and DEFAULT properties of the old field. If it has
changed, it will be handled separately.
"""
if field.db_default is not NOT_PROVIDED:
default_sql, params = self.db_default_sql(field)
default_sql %= tuple(self.quote_value(p) for p in params)
new_type += f" DEFAULT {default_sql}"
if field.null:
new_type += " NULL"
else:
@ -223,7 +227,7 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
def _alter_column_type_sql(
self, model, old_field, new_field, new_type, old_collation, new_collation
):
new_type = self._set_field_new_type_null_status(old_field, new_type)
new_type = self._set_field_new_type(old_field, new_type)
return super()._alter_column_type_sql(
model, old_field, new_field, new_type, old_collation, new_collation
)
@ -242,7 +246,7 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
return field_db_params["check"]
def _rename_field_sql(self, table, old_field, new_field, new_type):
new_type = self._set_field_new_type_null_status(old_field, new_type)
new_type = self._set_field_new_type(old_field, new_type)
return super()._rename_field_sql(table, old_field, new_field, new_type)
def _alter_column_comment_sql(self, model, new_field, new_type, new_db_comment):
@ -252,3 +256,18 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
def _comment_sql(self, comment):
comment_sql = super()._comment_sql(comment)
return f" COMMENT {comment_sql}"
def _alter_column_null_sql(self, model, old_field, new_field):
if new_field.db_default is NOT_PROVIDED:
return super()._alter_column_null_sql(model, old_field, new_field)
new_db_params = new_field.db_parameters(connection=self.connection)
type_sql = self._set_field_new_type(new_field, new_db_params["type"])
return (
"MODIFY %(column)s %(type)s"
% {
"column": self.quote_name(new_field.column),
"type": type_sql,
},
[],
)

4
django/db/backends/oracle/features.py
View File

@ -32,6 +32,7 @@ class DatabaseFeatures(BaseDatabaseFeatures):
atomic_transactions = False
nulls_order_largest = True
requires_literal_defaults = True
supports_default_keyword_in_bulk_insert = False
closed_cursor_error_class = InterfaceError
bare_select_suffix = " FROM DUAL"
# Select for update with limit can be achieved on Oracle, but not with the
@ -130,6 +131,9 @@ class DatabaseFeatures(BaseDatabaseFeatures):
"annotations.tests.NonAggregateAnnotationTestCase."
"test_custom_functions_can_ref_other_functions",
}
insert_test_table_with_defaults = (
"INSERT INTO {} VALUES (DEFAULT, DEFAULT, DEFAULT)"
)
@cached_property
def introspected_field_types(self):

2
django/db/backends/oracle/introspection.py
View File

@ -156,7 +156,7 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
field_map = {
column: (
display_size,
default if default != "NULL" else None,
default.rstrip() if default and default != "NULL" else None,
collation,
is_autofield,
is_json,

4
django/db/backends/oracle/schema.py
View File

@ -198,7 +198,9 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
return self.normalize_name(for_name + "_" + suffix)
def prepare_default(self, value):
return self.quote_value(value)
# Replace % with %% as %-formatting is applied in
# FormatStylePlaceholderCursor._fix_for_params().
return self.quote_value(value).replace("%", "%%")
def _field_should_be_indexed(self, model, field):
create_index = super()._field_should_be_indexed(model, field)

1
django/db/backends/postgresql/features.py
View File

@ -76,6 +76,7 @@ class DatabaseFeatures(BaseDatabaseFeatures):
"swedish_ci": "sv-x-icu",
}
test_now_utc_template = "STATEMENT_TIMESTAMP() AT TIME ZONE 'UTC'"
insert_test_table_with_defaults = "INSERT INTO {} DEFAULT VALUES"
django_test_skips = {
"opclasses are PostgreSQL only.": {

2
django/db/backends/sqlite3/features.py
View File

@ -59,6 +59,8 @@ class DatabaseFeatures(BaseDatabaseFeatures):
PRIMARY KEY(column_1, column_2)
)
"""
insert_test_table_with_defaults = 'INSERT INTO {} ("null") VALUES (1)'
supports_default_keyword_in_insert = False
@cached_property
def django_test_skips(self):

24
django/db/backends/sqlite3/schema.py
View File

@ -6,7 +6,7 @@ from django.db import NotSupportedError
from django.db.backends.base.schema import BaseDatabaseSchemaEditor
from django.db.backends.ddl_references import Statement
from django.db.backends.utils import strip_quotes
from django.db.models import UniqueConstraint
from django.db.models import NOT_PROVIDED, UniqueConstraint
from django.db.transaction import atomic
@ -233,9 +233,13 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
if create_field:
body[create_field.name] = create_field
# Choose a default and insert it into the copy map
if not create_field.many_to_many and create_field.concrete:
if (
create_field.db_default is NOT_PROVIDED
and not create_field.many_to_many
and create_field.concrete
):
mapping[create_field.column] = self.prepare_default(
self.effective_default(create_field),
self.effective_default(create_field)
)
# Add in any altered fields
for alter_field in alter_fields:
@ -244,9 +248,13 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
mapping.pop(old_field.column, None)
body[new_field.name] = new_field
if old_field.null and not new_field.null:
if new_field.db_default is NOT_PROVIDED:
default = self.prepare_default(self.effective_default(new_field))
else:
default, _ = self.db_default_sql(new_field)
case_sql = "coalesce(%(col)s, %(default)s)" % {
"col": self.quote_name(old_field.column),
"default": self.prepare_default(self.effective_default(new_field)),
"default": default,
}
mapping[new_field.column] = case_sql
else:
@ -381,6 +389,8 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
def add_field(self, model, field):
"""Create a field on a model."""
from django.db.models.expressions import Value
# Special-case implicit M2M tables.
if field.many_to_many and field.remote_field.through._meta.auto_created:
self.create_model(field.remote_field.through)
@ -394,6 +404,12 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
# COLUMN statement because DROP DEFAULT is not supported in
# ALTER TABLE.
or self.effective_default(field) is not None
# Fields with non-constant defaults cannot by handled by ALTER
# TABLE ADD COLUMN statement.
or (
field.db_default is not NOT_PROVIDED
and not isinstance(field.db_default, Value)
)
):
self._remake_table(model, create_field=field)
else:

2
django/db/migrations/autodetector.py
View File

@ -1040,6 +1040,7 @@ class MigrationAutodetector:
preserve_default = (
field.null
or field.has_default()
or field.db_default is not models.NOT_PROVIDED
or field.many_to_many
or (field.blank and field.empty_strings_allowed)
or (isinstance(field, time_fields) and field.auto_now)
@ -1187,6 +1188,7 @@ class MigrationAutodetector:
old_field.null
and not new_field.null
and not new_field.has_default()
and new_field.db_default is models.NOT_PROVIDED
and not new_field.many_to_many
):
field = new_field.clone()

6
django/db/models/base.py
View File

@ -971,8 +971,10 @@ class Model(AltersData, metaclass=ModelBase):
not raw
and not force_insert
and self._state.adding
and meta.pk.default
and meta.pk.default is not NOT_PROVIDED
and (
(meta.pk.default and meta.pk.default is not NOT_PROVIDED)
or (meta.pk.db_default and meta.pk.db_default is not NOT_PROVIDED)
)
):
force_insert = True
# If possible, try an UPDATE. If that doesn't update anything, do an INSERT.

37
django/db/models/expressions.py
View File

@ -176,6 +176,8 @@ class BaseExpression:
filterable = True
# Can the expression can be used as a source expression in Window?
window_compatible = False
# Can the expression be used as a database default value?
allowed_default = False
def __init__(self, output_field=None):
if output_field is not None:
@ -733,6 +735,10 @@ class CombinedExpression(SQLiteNumericMixin, Expression):
c.rhs = rhs
return c
@cached_property
def allowed_default(self):
return self.lhs.allowed_default and self.rhs.allowed_default
class DurationExpression(CombinedExpression):
def compile(self, side, compiler, connection):
@ -804,6 +810,8 @@ class TemporalSubtraction(CombinedExpression):
class F(Combinable):
"""An object capable of resolving references to existing query objects."""
allowed_default = False
def __init__(self, name):
"""
Arguments:
@ -987,6 +995,10 @@ class Func(SQLiteNumericMixin, Expression):
copy.extra = self.extra.copy()
return copy
@cached_property
def allowed_default(self):
return all(expression.allowed_default for expression in self.source_expressions)
@deconstructible(path="django.db.models.Value")
class Value(SQLiteNumericMixin, Expression):
@ -995,6 +1007,7 @@ class Value(SQLiteNumericMixin, Expression):
# Provide a default value for `for_save` in order to allow unresolved
# instances to be compiled until a decision is taken in #25425.
for_save = False
allowed_default = True
def __init__(self, value, output_field=None):
"""
@ -1069,6 +1082,8 @@ class Value(SQLiteNumericMixin, Expression):
class RawSQL(Expression):
allowed_default = True
def __init__(self, sql, params, output_field=None):
if output_field is None:
output_field = fields.Field()
@ -1110,6 +1125,13 @@ class Star(Expression):
return "*", []
class DatabaseDefault(Expression):
"""Placeholder expression for the database default in an insert query."""
def as_sql(self, compiler, connection):
return "DEFAULT", []
class Col(Expression):
contains_column_references = True
possibly_multivalued = False
@ -1213,6 +1235,7 @@ class ExpressionList(Func):
class OrderByList(Func):
allowed_default = False
template = "ORDER BY %(expressions)s"
def __init__(self, *expressions, **extra):
@ -1270,6 +1293,10 @@ class ExpressionWrapper(SQLiteNumericMixin, Expression):
def __repr__(self):
return "{}({})".format(self.__class__.__name__, self.expression)
@property
def allowed_default(self):
return self.expression.allowed_default
class NegatedExpression(ExpressionWrapper):
"""The logical negation of a conditional expression."""
@ -1397,6 +1424,10 @@ class When(Expression):
cols.extend(source.get_group_by_cols())
return cols
@cached_property
def allowed_default(self):
return self.condition.allowed_default and self.result.allowed_default
@deconstructible(path="django.db.models.Case")
class Case(SQLiteNumericMixin, Expression):
@ -1494,6 +1525,12 @@ class Case(SQLiteNumericMixin, Expression):
return self.default.get_group_by_cols()
return super().get_group_by_cols()
@cached_property
def allowed_default(self):
return self.default.allowed_default and all(
case_.allowed_default for case_ in self.cases
)
class Subquery(BaseExpression, Combinable):
"""

61
django/db/models/fields/__init__.py
View File

@ -202,6 +202,7 @@ class Field(RegisterLookupMixin):
validators=(),
error_messages=None,
db_comment=None,
db_default=NOT_PROVIDED,
):
self.name = name
self.verbose_name = verbose_name # May be set by set_attributes_from_name
@ -212,6 +213,13 @@ class Field(RegisterLookupMixin):
self.remote_field = rel
self.is_relation = self.remote_field is not None
self.default = default
if db_default is not NOT_PROVIDED and not hasattr(
db_default, "resolve_expression"
):
from django.db.models.expressions import Value
db_default = Value(db_default)
self.db_default = db_default
self.editable = editable
self.serialize = serialize
self.unique_for_date = unique_for_date
@ -263,6 +271,7 @@ class Field(RegisterLookupMixin):
return [
*self._check_field_name(),
*self._check_choices(),
*self._check_db_default(**kwargs),
*self._check_db_index(),
*self._check_db_comment(**kwargs),
*self._check_null_allowed_for_primary_keys(),
@ -379,6 +388,39 @@ class Field(RegisterLookupMixin):
)
]
def _check_db_default(self, databases=None, **kwargs):
from django.db.models.expressions import Value
if (
self.db_default is NOT_PROVIDED
or isinstance(self.db_default, Value)
or databases is None
):
return []
errors = []
for db in databases:
if not router.allow_migrate_model(db, self.model):
continue
connection = connections[db]
if not getattr(self.db_default, "allowed_default", False) and (
connection.features.supports_expression_defaults
):
msg = f"{self.db_default} cannot be used in db_default."
errors.append(checks.Error(msg, obj=self, id="fields.E012"))
if not (
connection.features.supports_expression_defaults
or "supports_expression_defaults"
in self.model._meta.required_db_features
):
msg = (
f"{connection.display_name} does not support default database "
"values with expressions (db_default)."
)
errors.append(checks.Error(msg, obj=self, id="fields.E011"))
return errors
def _check_db_index(self):
if self.db_index not in (None, True, False):
return [
@ -558,6 +600,7 @@ class Field(RegisterLookupMixin):
"null": False,
"db_index": False,
"default": NOT_PROVIDED,
"db_default": NOT_PROVIDED,
"editable": True,
"serialize": True,
"unique_for_date": None,
@ -876,7 +919,10 @@ class Field(RegisterLookupMixin):
@property
def db_returning(self):
"""Private API intended only to be used by Django itself."""
return False
return (
self.db_default is not NOT_PROVIDED
and connection.features.can_return_columns_from_insert
)
def set_attributes_from_name(self, name):
self.name = self.name or name
@ -929,7 +975,13 @@ class Field(RegisterLookupMixin):
def pre_save(self, model_instance, add):
"""Return field's value just before saving."""
return getattr(model_instance, self.attname)
value = getattr(model_instance, self.attname)
if not connection.features.supports_default_keyword_in_insert:
from django.db.models.expressions import DatabaseDefault
if isinstance(value, DatabaseDefault):
return self.db_default
return value
def get_prep_value(self, value):
"""Perform preliminary non-db specific value checks and conversions."""
@ -968,6 +1020,11 @@ class Field(RegisterLookupMixin):
return self.default
return lambda: self.default
if self.db_default is not NOT_PROVIDED:
from django.db.models.expressions import DatabaseDefault
return DatabaseDefault
if (
not self.empty_strings_allowed
or self.null

1
django/db/models/functions/comparison.py
View File

@ -105,6 +105,7 @@ class Coalesce(Func):
class Collate(Func):
function = "COLLATE"
template = "%(expressions)s %(function)s %(collation)s"
allowed_default = False
# Inspired from
# https://www.postgresql.org/docs/current/sql-syntax-lexical.html#SQL-SYNTAX-IDENTIFIERS
collation_re = _lazy_re_compile(r"^[\w\-]+$")

4
django/db/models/lookups.py
View File

@ -185,6 +185,10 @@ class Lookup(Expression):
sql = f"CASE WHEN {sql} THEN 1 ELSE 0 END"
return sql, params
@cached_property
def allowed_default(self):
return self.lhs.allowed_default and self.rhs.allowed_default
class Transform(RegisterLookupMixin, Func):
"""

9
django/db/models/query.py
View File

@ -654,10 +654,19 @@ class QuerySet(AltersData):
return await sync_to_async(self.create)(**kwargs)
def _prepare_for_bulk_create(self, objs):
from django.db.models.expressions import DatabaseDefault
connection = connections[self.db]
for obj in objs:
if obj.pk is None:
# Populate new PK values.
obj.pk = obj._meta.pk.get_pk_value_on_save(obj)
if not connection.features.supports_default_keyword_in_bulk_insert:
for field in obj._meta.fields:
value = getattr(obj, field.attname)
if isinstance(value, DatabaseDefault):
setattr(obj, field.attname, field.db_default)
obj._prepare_related_fields_for_save(operation_name="bulk_create")
def _check_bulk_create_options(

3
docs/ref/checks.txt
View File

@ -175,6 +175,9 @@ Model fields
``choices`` (``<count>`` characters).
* **fields.E010**: ``<field>`` default should be a callable instead of an
instance so that it's not shared between all field instances.
* **fields.E011**: ``<database>`` does not support default database values with
expressions (``db_default``).
* **fields.E012**: ``<expression>`` cannot be used in ``db_default``.
* **fields.E100**: ``AutoField``\s must set primary_key=True.
* **fields.E110**: ``BooleanField``\s do not accept null values. *This check
appeared before support for null values was added in Django 2.1.*

7
docs/ref/models/expressions.txt
View File

@ -996,6 +996,13 @@ calling the appropriate methods on the wrapped expression.
.. class:: Expression
.. attribute:: allowed_default
.. versionadded:: 5.0
Tells Django that this expression can be used in
:attr:`Field.db_default`. Defaults to ``False``.
.. attribute:: contains_aggregate
Tells Django that this expression contains an aggregate and that a

35
docs/ref/models/fields.txt
View File

@ -351,6 +351,38 @@ looking at your Django code. For example::
db_comment="Date and time when the article was published",
)
``db_default``
--------------
.. versionadded:: 5.0
.. attribute:: Field.db_default
The database-computed default value for this field. This can be a literal value
or a database function, such as :class:`~django.db.models.functions.Now`::
created = models.DateTimeField(db_default=Now())
More complex expressions can be used, as long as they are made from literals
and database functions::
month_due = models.DateField(
db_default=TruncMonth(
Now() + timedelta(days=90),
output_field=models.DateField(),
)
)
Database defaults cannot reference other fields or models. For example, this is
invalid::
end = models.IntegerField(db_default=F("start") + 50)
If both ``db_default`` and :attr:`Field.default` are set, ``default`` will take
precedence when creating instances in Python code. ``db_default`` will still be
set at the database level and will be used when inserting rows outside of the
ORM or when adding a new field in a migration.
``db_index``
------------
@ -408,6 +440,9 @@ The default value is used when new model instances are created and a value
isn't provided for the field. When the field is a primary key, the default is
also used when the field is set to ``None``.
The default value can also be set at the database level with
:attr:`Field.db_default`.
``editable``
------------

14
docs/ref/models/instances.txt
View File

@ -541,7 +541,8 @@ You may have noticed Django database objects use the same ``save()`` method
for creating and changing objects. Django abstracts the need to use ``INSERT``
or ``UPDATE`` SQL statements. Specifically, when you call ``save()`` and the
object's primary key attribute does **not** define a
:attr:`~django.db.models.Field.default`, Django follows this algorithm:
:attr:`~django.db.models.Field.default` or
:attr:`~django.db.models.Field.db_default`, Django follows this algorithm:
* If the object's primary key attribute is set to a value that evaluates to
``True`` (i.e., a value other than ``None`` or the empty string), Django
@ -551,9 +552,10 @@ object's primary key attribute does **not** define a
exist in the database), Django executes an ``INSERT``.
If the object's primary key attribute defines a
:attr:`~django.db.models.Field.default` then Django executes an ``UPDATE`` if
it is an existing model instance and primary key is set to a value that exists
in the database. Otherwise, Django executes an ``INSERT``.
:attr:`~django.db.models.Field.default` or
:attr:`~django.db.models.Field.db_default` then Django executes an ``UPDATE``
if it is an existing model instance and primary key is set to a value that
exists in the database. Otherwise, Django executes an ``INSERT``.
The one gotcha here is that you should be careful not to specify a primary-key
value explicitly when saving new objects, if you cannot guarantee the
@ -570,6 +572,10 @@ which returns ``NULL``. In such cases it is possible to revert to the old
algorithm by setting the :attr:`~django.db.models.Options.select_on_save`
option to ``True``.
.. versionchanged:: 5.0
The ``Field.db_default`` parameter was added.
.. _ref-models-force-insert:
Forcing an INSERT or UPDATE

26
docs/releases/5.0.txt
View File

@ -108,6 +108,21 @@ Can now be simplified to:
per-project, per-field, or per-request basis. See
:ref:`reusable-field-group-templates`.
Database-computed default values
--------------------------------
The new :attr:`Field.db_default <django.db.models.Field.db_default>` parameter
sets a database-computed default value. For example::
from django.db import models
from django.db.models.functions import Now, Pi
class MyModel(models.Model):
age = models.IntegerField(db_default=18)
created = models.DateTimeField(db_default=Now())
circumference = models.FloatField(db_default=2 * Pi())
Minor features
--------------
@ -355,7 +370,16 @@ Database backend API
This section describes changes that may be needed in third-party database
backends.
* ...
* ``DatabaseFeatures.supports_expression_defaults`` should be set to ``False``
if the database doesn't support using database functions as defaults.
* ``DatabaseFeatures.supports_default_keyword_in_insert`` should be set to
``False`` if the database doesn't support the ``DEFAULT`` keyword in
``INSERT`` queries.
* ``DatabaseFeatures.supports_default_keyword_in_bulk insert`` should be set to
``False`` if the database doesn't support the ``DEFAULT`` keyword in bulk
``INSERT`` queries.
Using ``create_defaults__exact`` may now be required with ``QuerySet.update_or_create()``
-----------------------------------------------------------------------------------------

4
tests/basic/models.py
View File

@ -49,5 +49,9 @@ class PrimaryKeyWithDefault(models.Model):
uuid = models.UUIDField(primary_key=True, default=uuid.uuid4)
class PrimaryKeyWithDbDefault(models.Model):
uuid = models.IntegerField(primary_key=True, db_default=1)
class ChildPrimaryKeyWithDefault(PrimaryKeyWithDefault):
pass

6
tests/basic/tests.py
View File

@ -20,6 +20,7 @@ from .models import (
ArticleSelectOnSave,
ChildPrimaryKeyWithDefault,
FeaturedArticle,
PrimaryKeyWithDbDefault,
PrimaryKeyWithDefault,
SelfRef,
)
@ -175,6 +176,11 @@ class ModelInstanceCreationTests(TestCase):
with self.assertNumQueries(1):
PrimaryKeyWithDefault().save()
def test_save_primary_with_db_default(self):
# An UPDATE attempt is skipped when a primary key has db_default.
with self.assertNumQueries(1):
PrimaryKeyWithDbDefault().save()
def test_save_parent_primary_with_default(self):
# An UPDATE attempt is skipped when an inherited primary key has
# default.

44
tests/field_defaults/models.py
View File

@ -12,6 +12,8 @@ field.
from datetime import datetime
from django.db import models
from django.db.models.functions import Coalesce, ExtractYear, Now, Pi
from django.db.models.lookups import GreaterThan
class Article(models.Model):
@ -20,3 +22,45 @@ class Article(models.Model):
def __str__(self):
return self.headline
class DBArticle(models.Model):
"""
Values or expressions can be passed as the db_default parameter to a field.
When the object is created without an explicit value passed in, the
database will insert the default value automatically.
"""
headline = models.CharField(max_length=100, db_default="Default headline")
pub_date = models.DateTimeField(db_default=Now())
class Meta:
required_db_features = {"supports_expression_defaults"}
class DBDefaults(models.Model):
both = models.IntegerField(default=1, db_default=2)
null = models.FloatField(null=True, db_default=1.1)
class DBDefaultsFunction(models.Model):
number = models.FloatField(db_default=Pi())
year = models.IntegerField(db_default=ExtractYear(Now()))
added = models.FloatField(db_default=Pi() + 4.5)
multiple_subfunctions = models.FloatField(db_default=Coalesce(4.5, Pi()))
case_when = models.IntegerField(
db_default=models.Case(models.When(GreaterThan(2, 1), then=3), default=4)
)
class Meta:
required_db_features = {"supports_expression_defaults"}
class DBDefaultsPK(models.Model):
language_code = models.CharField(primary_key=True, max_length=2, db_default="en")
class DBDefaultsFK(models.Model):
language_code = models.ForeignKey(
DBDefaultsPK, db_default="fr", on_delete=models.CASCADE
)

192
tests/field_defaults/tests.py
View File

@ -1,8 +1,28 @@
from datetime import datetime
from math import pi
from django.test import TestCase
from django.db import connection
from django.db.models import Case, F, FloatField, Value, When
from django.db.models.expressions import (
Expression,
ExpressionList,
ExpressionWrapper,
Func,
OrderByList,
RawSQL,
)
from django.db.models.functions import Collate
from django.db.models.lookups import GreaterThan
from django.test import SimpleTestCase, TestCase, skipIfDBFeature, skipUnlessDBFeature
from .models import Article
from .models import (
Article,
DBArticle,
DBDefaults,
DBDefaultsFK,
DBDefaultsFunction,
DBDefaultsPK,
)
class DefaultTests(TestCase):
@ -14,3 +34,171 @@ class DefaultTests(TestCase):
self.assertIsInstance(a.id, int)
self.assertEqual(a.headline, "Default headline")
self.assertLess((now - a.pub_date).seconds, 5)
@skipUnlessDBFeature(
"can_return_columns_from_insert", "supports_expression_defaults"
)
def test_field_db_defaults_returning(self):
a = DBArticle()
a.save()
self.assertIsInstance(a.id, int)
self.assertEqual(a.headline, "Default headline")
self.assertIsInstance(a.pub_date, datetime)
@skipIfDBFeature("can_return_columns_from_insert")
@skipUnlessDBFeature("supports_expression_defaults")
def test_field_db_defaults_refresh(self):
a = DBArticle()
a.save()
a.refresh_from_db()
self.assertIsInstance(a.id, int)
self.assertEqual(a.headline, "Default headline")
self.assertIsInstance(a.pub_date, datetime)
def test_null_db_default(self):
obj1 = DBDefaults.objects.create()
if not connection.features.can_return_columns_from_insert:
obj1.refresh_from_db()
self.assertEqual(obj1.null, 1.1)
obj2 = DBDefaults.objects.create(null=None)
self.assertIsNone(obj2.null)
@skipUnlessDBFeature("supports_expression_defaults")
def test_db_default_function(self):
m = DBDefaultsFunction.objects.create()
if not connection.features.can_return_columns_from_insert:
m.refresh_from_db()
self.assertAlmostEqual(m.number, pi)
self.assertEqual(m.year, datetime.now().year)
self.assertAlmostEqual(m.added, pi + 4.5)
self.assertEqual(m.multiple_subfunctions, 4.5)
@skipUnlessDBFeature("insert_test_table_with_defaults")
def test_both_default(self):
create_sql = connection.features.insert_test_table_with_defaults
with connection.cursor() as cursor:
cursor.execute(create_sql.format(DBDefaults._meta.db_table))
obj1 = DBDefaults.objects.get()
self.assertEqual(obj1.both, 2)
obj2 = DBDefaults.objects.create()
self.assertEqual(obj2.both, 1)
def test_pk_db_default(self):
obj1 = DBDefaultsPK.objects.create()
if not connection.features.can_return_columns_from_insert:
# refresh_from_db() cannot be used because that needs the pk to
# already be known to Django.
obj1 = DBDefaultsPK.objects.get(pk="en")
self.assertEqual(obj1.pk, "en")
self.assertEqual(obj1.language_code, "en")
obj2 = DBDefaultsPK.objects.create(language_code="de")
self.assertEqual(obj2.pk, "de")
self.assertEqual(obj2.language_code, "de")
def test_foreign_key_db_default(self):
parent1 = DBDefaultsPK.objects.create(language_code="fr")
child1 = DBDefaultsFK.objects.create()
if not connection.features.can_return_columns_from_insert:
child1.refresh_from_db()
self.assertEqual(child1.language_code, parent1)
parent2 = DBDefaultsPK.objects.create()
if not connection.features.can_return_columns_from_insert:
# refresh_from_db() cannot be used because that needs the pk to
# already be known to Django.
parent2 = DBDefaultsPK.objects.get(pk="en")
child2 = DBDefaultsFK.objects.create(language_code=parent2)
self.assertEqual(child2.language_code, parent2)
@skipUnlessDBFeature(
"can_return_columns_from_insert", "supports_expression_defaults"
)
def test_case_when_db_default_returning(self):
m = DBDefaultsFunction.objects.create()
self.assertEqual(m.case_when, 3)
@skipIfDBFeature("can_return_columns_from_insert")
@skipUnlessDBFeature("supports_expression_defaults")
def test_case_when_db_default_no_returning(self):
m = DBDefaultsFunction.objects.create()
m.refresh_from_db()
self.assertEqual(m.case_when, 3)
@skipUnlessDBFeature("supports_expression_defaults")
def test_bulk_create_all_db_defaults(self):
articles = [DBArticle(), DBArticle()]
DBArticle.objects.bulk_create(articles)
headlines = DBArticle.objects.values_list("headline", flat=True)
self.assertSequenceEqual(headlines, ["Default headline", "Default headline"])
@skipUnlessDBFeature("supports_expression_defaults")
def test_bulk_create_all_db_defaults_one_field(self):
pub_date = datetime.now()
articles = [DBArticle(pub_date=pub_date), DBArticle(pub_date=pub_date)]
DBArticle.objects.bulk_create(articles)
headlines = DBArticle.objects.values_list("headline", "pub_date")
self.assertSequenceEqual(
headlines,
[
("Default headline", pub_date),
("Default headline", pub_date),
],
)
@skipUnlessDBFeature("supports_expression_defaults")
def test_bulk_create_mixed_db_defaults(self):
articles = [DBArticle(), DBArticle(headline="Something else")]
DBArticle.objects.bulk_create(articles)
headlines = DBArticle.objects.values_list("headline", flat=True)
self.assertCountEqual(headlines, ["Default headline", "Something else"])
@skipUnlessDBFeature("supports_expression_defaults")
def test_bulk_create_mixed_db_defaults_function(self):
instances = [DBDefaultsFunction(), DBDefaultsFunction(year=2000)]
DBDefaultsFunction.objects.bulk_create(instances)
years = DBDefaultsFunction.objects.values_list("year", flat=True)
self.assertCountEqual(years, [2000, datetime.now().year])
class AllowedDefaultTests(SimpleTestCase):
def test_allowed(self):
class Max(Func):
function = "MAX"
tests = [
Value(10),
Max(1, 2),
RawSQL("Now()", ()),
Value(10) + Value(7), # Combined expression.
ExpressionList(Value(1), Value(2)),
ExpressionWrapper(Value(1), output_field=FloatField()),
Case(When(GreaterThan(2, 1), then=3), default=4),
]
for expression in tests:
with self.subTest(expression=expression):
self.assertIs(expression.allowed_default, True)
def test_disallowed(self):
class Max(Func):
function = "MAX"
tests = [
Expression(),
F("field"),
Max(F("count"), 1),
Value(10) + F("count"), # Combined expression.
ExpressionList(F("count"), Value(2)),
ExpressionWrapper(F("count"), output_field=FloatField()),
Collate(Value("John"), "nocase"),
OrderByList("field"),
]
for expression in tests:
with self.subTest(expression=expression):
self.assertIs(expression.allowed_default, False)

107
tests/invalid_models_tests/test_ordinary_fields.py
View File

@ -4,6 +4,7 @@ import uuid
from django.core.checks import Error
from django.core.checks import Warning as DjangoWarning
from django.db import connection, models
from django.db.models.functions import Coalesce, Pi
from django.test import SimpleTestCase, TestCase, skipIfDBFeature, skipUnlessDBFeature
from django.test.utils import isolate_apps, override_settings
from django.utils.functional import lazy
@ -1057,3 +1058,109 @@ class DbCommentTests(TestCase):
errors = Model._meta.get_field("field").check(databases=self.databases)
self.assertEqual(errors, [])
@isolate_apps("invalid_models_tests")
class InvalidDBDefaultTests(TestCase):
def test_db_default(self):
class Model(models.Model):
field = models.FloatField(db_default=Pi())
field = Model._meta.get_field("field")
errors = field.check(databases=self.databases)
if connection.features.supports_expression_defaults:
expected_errors = []
else:
msg = (
f"{connection.display_name} does not support default database values "
"with expressions (db_default)."
)
expected_errors = [Error(msg=msg, obj=field, id="fields.E011")]
self.assertEqual(errors, expected_errors)
def test_db_default_literal(self):
class Model(models.Model):
field = models.IntegerField(db_default=1)
field = Model._meta.get_field("field")
errors = field.check(databases=self.databases)
self.assertEqual(errors, [])
def test_db_default_required_db_features(self):
class Model(models.Model):
field = models.FloatField(db_default=Pi())
class Meta:
required_db_features = {"supports_expression_defaults"}
field = Model._meta.get_field("field")
errors = field.check(databases=self.databases)
self.assertEqual(errors, [])
def test_db_default_expression_invalid(self):
expression = models.F("field_name")
class Model(models.Model):
field = models.FloatField(db_default=expression)
field = Model._meta.get_field("field")
errors = field.check(databases=self.databases)
if connection.features.supports_expression_defaults:
msg = f"{expression} cannot be used in db_default."
expected_errors = [Error(msg=msg, obj=field, id="fields.E012")]
else:
msg = (
f"{connection.display_name} does not support default database values "
"with expressions (db_default)."
)
expected_errors = [Error(msg=msg, obj=field, id="fields.E011")]
self.assertEqual(errors, expected_errors)
def test_db_default_expression_required_db_features(self):
expression = models.F("field_name")
class Model(models.Model):
field = models.FloatField(db_default=expression)
class Meta:
required_db_features = {"supports_expression_defaults"}
field = Model._meta.get_field("field")
errors = field.check(databases=self.databases)
if connection.features.supports_expression_defaults:
msg = f"{expression} cannot be used in db_default."
expected_errors = [Error(msg=msg, obj=field, id="fields.E012")]
else:
expected_errors = []
self.assertEqual(errors, expected_errors)
@skipUnlessDBFeature("supports_expression_defaults")
def test_db_default_combined_invalid(self):
expression = models.Value(4.5) + models.F("field_name")
class Model(models.Model):
field = models.FloatField(db_default=expression)
field = Model._meta.get_field("field")
errors = field.check(databases=self.databases)
msg = f"{expression} cannot be used in db_default."
expected_error = Error(msg=msg, obj=field, id="fields.E012")
self.assertEqual(errors, [expected_error])
@skipUnlessDBFeature("supports_expression_defaults")
def test_db_default_function_arguments_invalid(self):
expression = Coalesce(models.Value(4.5), models.F("field_name"))
class Model(models.Model):
field = models.FloatField(db_default=expression)
field = Model._meta.get_field("field")
errors = field.check(databases=self.databases)
msg = f"{expression} cannot be used in db_default."
expected_error = Error(msg=msg, obj=field, id="fields.E012")
self.assertEqual(errors, [expected_error])

40
tests/migrations/test_autodetector.py
View File

@ -269,6 +269,14 @@ class AutodetectorTests(BaseAutodetectorTests):
("name", models.CharField(max_length=200, default="Ada Lovelace")),
],
)
author_name_db_default = ModelState(
"testapp",
"Author",
[
("id", models.AutoField(primary_key=True)),
("name", models.CharField(max_length=200, db_default="Ada Lovelace")),
],
)
author_name_check_constraint = ModelState(
"testapp",
"Author",
@ -1289,6 +1297,21 @@ class AutodetectorTests(BaseAutodetectorTests):
self.assertOperationTypes(changes, "testapp", 0, ["AddField"])
self.assertOperationAttributes(changes, "testapp", 0, 0, name="name")
@mock.patch(
"django.db.migrations.questioner.MigrationQuestioner.ask_not_null_addition",
side_effect=AssertionError("Should not have prompted for not null addition"),
)
def test_add_not_null_field_with_db_default(self, mocked_ask_method):
changes = self.get_changes([self.author_empty], [self.author_name_db_default])
self.assertNumberMigrations(changes, "testapp", 1)
self.assertOperationTypes(changes, "testapp", 0, ["AddField"])
self.assertOperationAttributes(
changes, "testapp", 0, 0, name="name", preserve_default=True
)
self.assertOperationFieldAttributes(
changes, "testapp", 0, 0, db_default=models.Value("Ada Lovelace")
)
@mock.patch(
"django.db.migrations.questioner.MigrationQuestioner.ask_not_null_addition",
side_effect=AssertionError("Should not have prompted for not null addition"),
@ -1478,6 +1501,23 @@ class AutodetectorTests(BaseAutodetectorTests):
changes, "testapp", 0, 0, default="Ada Lovelace"
)
@mock.patch(
"django.db.migrations.questioner.MigrationQuestioner.ask_not_null_alteration",
side_effect=AssertionError("Should not have prompted for not null alteration"),
)
def test_alter_field_to_not_null_with_db_default(self, mocked_ask_method):
changes = self.get_changes(
[self.author_name_null], [self.author_name_db_default]
)
self.assertNumberMigrations(changes, "testapp", 1)
self.assertOperationTypes(changes, "testapp", 0, ["AlterField"])
self.assertOperationAttributes(
changes, "testapp", 0, 0, name="name", preserve_default=True
)
self.assertOperationFieldAttributes(
changes, "testapp", 0, 0, db_default=models.Value("Ada Lovelace")
)
@mock.patch(
"django.db.migrations.questioner.MigrationQuestioner.ask_not_null_alteration",
return_value=models.NOT_PROVIDED,

7
tests/migrations/test_base.py
View File

@ -292,6 +292,13 @@ class OperationTestBase(MigrationTestBase):
("id", models.AutoField(primary_key=True)),
("pink", models.IntegerField(default=3)),
("weight", models.FloatField()),
("green", models.IntegerField(null=True)),
(
"yellow",
models.CharField(
blank=True, null=True, db_default="Yellow", max_length=20
),
),
],
options=model_options,
)

317
tests/migrations/test_operations.py
View File

@ -1,14 +1,18 @@
import math
from django.core.exceptions import FieldDoesNotExist
from django.db import IntegrityError, connection, migrations, models, transaction
from django.db.migrations.migration import Migration
from django.db.migrations.operations.fields import FieldOperation
from django.db.migrations.state import ModelState, ProjectState
from django.db.models.functions import Abs
from django.db.models.expressions import Value
from django.db.models.functions import Abs, Pi
from django.db.transaction import atomic
from django.test import (
SimpleTestCase,
ignore_warnings,
override_settings,
skipIfDBFeature,
skipUnlessDBFeature,
)
from django.test.utils import CaptureQueriesContext
@ -1340,7 +1344,7 @@ class OperationTests(OperationTestBase):
self.assertEqual(operation.describe(), "Add field height to Pony")
self.assertEqual(operation.migration_name_fragment, "pony_height")
project_state, new_state = self.make_test_state("test_adfl", operation)
self.assertEqual(len(new_state.models["test_adfl", "pony"].fields), 4)
self.assertEqual(len(new_state.models["test_adfl", "pony"].fields), 6)
field = new_state.models["test_adfl", "pony"].fields["height"]
self.assertEqual(field.default, 5)
# Test the database alteration
@ -1528,7 +1532,7 @@ class OperationTests(OperationTestBase):
)
new_state = project_state.clone()
operation.state_forwards("test_adflpd", new_state)
self.assertEqual(len(new_state.models["test_adflpd", "pony"].fields), 4)
self.assertEqual(len(new_state.models["test_adflpd", "pony"].fields), 6)
field = new_state.models["test_adflpd", "pony"].fields["height"]
self.assertEqual(field.default, models.NOT_PROVIDED)
# Test the database alteration
@ -1547,6 +1551,169 @@ class OperationTests(OperationTestBase):
sorted(definition[2]), ["field", "model_name", "name", "preserve_default"]
)
def test_add_field_database_default(self):
"""The AddField operation can set and unset a database default."""
app_label = "test_adfldd"
table_name = f"{app_label}_pony"
project_state = self.set_up_test_model(app_label)
operation = migrations.AddField(
"Pony", "height", models.FloatField(null=True, db_default=4)
)
new_state = project_state.clone()
operation.state_forwards(app_label, new_state)
self.assertEqual(len(new_state.models[app_label, "pony"].fields), 6)
field = new_state.models[app_label, "pony"].fields["height"]
self.assertEqual(field.default, models.NOT_PROVIDED)
self.assertEqual(field.db_default, Value(4))
project_state.apps.get_model(app_label, "pony").objects.create(weight=4)
self.assertColumnNotExists(table_name, "height")
# Add field.
with connection.schema_editor() as editor:
operation.database_forwards(app_label, editor, project_state, new_state)
self.assertColumnExists(table_name, "height")
new_model = new_state.apps.get_model(app_label, "pony")
old_pony = new_model.objects.get()
self.assertEqual(old_pony.height, 4)
new_pony = new_model.objects.create(weight=5)
if not connection.features.can_return_columns_from_insert:
new_pony.refresh_from_db()
self.assertEqual(new_pony.height, 4)
# Reversal.
with connection.schema_editor() as editor:
operation.database_backwards(app_label, editor, new_state, project_state)
self.assertColumnNotExists(table_name, "height")
# Deconstruction.
definition = operation.deconstruct()
self.assertEqual(definition[0], "AddField")
self.assertEqual(definition[1], [])
self.assertEqual(
definition[2],
{
"field": field,
"model_name": "Pony",
"name": "height",
},
)
def test_add_field_database_default_special_char_escaping(self):
app_label = "test_adflddsce"
table_name = f"{app_label}_pony"
project_state = self.set_up_test_model(app_label)
old_pony_pk = (
project_state.apps.get_model(app_label, "pony").objects.create(weight=4).pk
)
tests = ["%", "'", '"']
for db_default in tests:
with self.subTest(db_default=db_default):
operation = migrations.AddField(
"Pony",
"special_char",
models.CharField(max_length=1, db_default=db_default),
)
new_state = project_state.clone()
operation.state_forwards(app_label, new_state)
self.assertEqual(len(new_state.models[app_label, "pony"].fields), 6)
field = new_state.models[app_label, "pony"].fields["special_char"]
self.assertEqual(field.default, models.NOT_PROVIDED)
self.assertEqual(field.db_default, Value(db_default))
self.assertColumnNotExists(table_name, "special_char")
with connection.schema_editor() as editor:
operation.database_forwards(
app_label, editor, project_state, new_state
)
self.assertColumnExists(table_name, "special_char")
new_model = new_state.apps.get_model(app_label, "pony")
try:
new_pony = new_model.objects.create(weight=5)
if not connection.features.can_return_columns_from_insert:
new_pony.refresh_from_db()
self.assertEqual(new_pony.special_char, db_default)
old_pony = new_model.objects.get(pk=old_pony_pk)
if connection.vendor != "oracle" or db_default != "'":
# The single quotation mark ' is properly quoted and is
# set for new rows on Oracle, however it is not set on
# existing rows. Skip the assertion as it's probably a
# bug in Oracle.
self.assertEqual(old_pony.special_char, db_default)
finally:
with connection.schema_editor() as editor:
operation.database_backwards(
app_label, editor, new_state, project_state
)
@skipUnlessDBFeature("supports_expression_defaults")
def test_add_field_database_default_function(self):
app_label = "test_adflddf"
table_name = f"{app_label}_pony"
project_state = self.set_up_test_model(app_label)
operation = migrations.AddField(
"Pony", "height", models.FloatField(db_default=Pi())
)
new_state = project_state.clone()
operation.state_forwards(app_label, new_state)
self.assertEqual(len(new_state.models[app_label, "pony"].fields), 6)
field = new_state.models[app_label, "pony"].fields["height"]
self.assertEqual(field.default, models.NOT_PROVIDED)
self.assertEqual(field.db_default, Pi())
project_state.apps.get_model(app_label, "pony").objects.create(weight=4)
self.assertColumnNotExists(table_name, "height")
# Add field.
with connection.schema_editor() as editor:
operation.database_forwards(app_label, editor, project_state, new_state)
self.assertColumnExists(table_name, "height")
new_model = new_state.apps.get_model(app_label, "pony")
old_pony = new_model.objects.get()
self.assertAlmostEqual(old_pony.height, math.pi)
new_pony = new_model.objects.create(weight=5)
if not connection.features.can_return_columns_from_insert:
new_pony.refresh_from_db()
self.assertAlmostEqual(old_pony.height, math.pi)
def test_add_field_both_defaults(self):
"""The AddField operation with both default and db_default."""
app_label = "test_adflbddd"
table_name = f"{app_label}_pony"
project_state = self.set_up_test_model(app_label)
operation = migrations.AddField(
"Pony", "height", models.FloatField(default=3, db_default=4)
)
new_state = project_state.clone()
operation.state_forwards(app_label, new_state)
self.assertEqual(len(new_state.models[app_label, "pony"].fields), 6)
field = new_state.models[app_label, "pony"].fields["height"]
self.assertEqual(field.default, 3)
self.assertEqual(field.db_default, Value(4))
project_state.apps.get_model(app_label, "pony").objects.create(weight=4)
self.assertColumnNotExists(table_name, "height")
# Add field.
with connection.schema_editor() as editor:
operation.database_forwards(app_label, editor, project_state, new_state)
self.assertColumnExists(table_name, "height")
new_model = new_state.apps.get_model(app_label, "pony")
old_pony = new_model.objects.get()
self.assertEqual(old_pony.height, 4)
new_pony = new_model.objects.create(weight=5)
if not connection.features.can_return_columns_from_insert:
new_pony.refresh_from_db()
self.assertEqual(new_pony.height, 3)
# Reversal.
with connection.schema_editor() as editor:
operation.database_backwards(app_label, editor, new_state, project_state)
self.assertColumnNotExists(table_name, "height")
# Deconstruction.
definition = operation.deconstruct()
self.assertEqual(definition[0], "AddField")
self.assertEqual(definition[1], [])
self.assertEqual(
definition[2],
{
"field": field,
"model_name": "Pony",
"name": "height",
},
)
def test_add_field_m2m(self):
"""
Tests the AddField operation with a ManyToManyField.
@ -1558,7 +1725,7 @@ class OperationTests(OperationTestBase):
)
new_state = project_state.clone()
operation.state_forwards("test_adflmm", new_state)
self.assertEqual(len(new_state.models["test_adflmm", "pony"].fields), 4)
self.assertEqual(len(new_state.models["test_adflmm", "pony"].fields), 6)
# Test the database alteration
self.assertTableNotExists("test_adflmm_pony_stables")
with connection.schema_editor() as editor:
@ -1727,7 +1894,7 @@ class OperationTests(OperationTestBase):
self.assertEqual(operation.migration_name_fragment, "remove_pony_pink")
new_state = project_state.clone()
operation.state_forwards("test_rmfl", new_state)
self.assertEqual(len(new_state.models["test_rmfl", "pony"].fields), 2)
self.assertEqual(len(new_state.models["test_rmfl", "pony"].fields), 4)
# Test the database alteration
self.assertColumnExists("test_rmfl_pony", "pink")
with connection.schema_editor() as editor:
@ -1934,6 +2101,146 @@ class OperationTests(OperationTestBase):
self.assertEqual(definition[1], [])
self.assertEqual(sorted(definition[2]), ["field", "model_name", "name"])
def test_alter_field_add_database_default(self):
app_label = "test_alfladd"
project_state = self.set_up_test_model(app_label)
operation = migrations.AlterField(
"Pony", "weight", models.FloatField(db_default=4.5)
)
new_state = project_state.clone()
operation.state_forwards(app_label, new_state)
old_weight = project_state.models[app_label, "pony"].fields["weight"]
self.assertIs(old_weight.db_default, models.NOT_PROVIDED)
new_weight = new_state.models[app_label, "pony"].fields["weight"]
self.assertEqual(new_weight.db_default, Value(4.5))
with self.assertRaises(IntegrityError), transaction.atomic():
project_state.apps.get_model(app_label, "pony").objects.create()
# Alter field.
with connection.schema_editor() as editor:
operation.database_forwards(app_label, editor, project_state, new_state)
pony = new_state.apps.get_model(app_label, "pony").objects.create()
if not connection.features.can_return_columns_from_insert:
pony.refresh_from_db()
self.assertEqual(pony.weight, 4.5)
# Reversal.
with connection.schema_editor() as editor:
operation.database_backwards(app_label, editor, new_state, project_state)
with self.assertRaises(IntegrityError), transaction.atomic():
project_state.apps.get_model(app_label, "pony").objects.create()
# Deconstruction.
definition = operation.deconstruct()
self.assertEqual(definition[0], "AlterField")
self.assertEqual(definition[1], [])
self.assertEqual(
definition[2],
{
"field": new_weight,
"model_name": "Pony",
"name": "weight",
},
)
def test_alter_field_change_default_to_database_default(self):
"""The AlterField operation changing default to db_default."""
app_label = "test_alflcdtdd"
project_state = self.set_up_test_model(app_label)
operation = migrations.AlterField(
"Pony", "pink", models.IntegerField(db_default=4)
)
new_state = project_state.clone()
operation.state_forwards(app_label, new_state)
old_pink = project_state.models[app_label, "pony"].fields["pink"]
self.assertEqual(old_pink.default, 3)
self.assertIs(old_pink.db_default, models.NOT_PROVIDED)
new_pink = new_state.models[app_label, "pony"].fields["pink"]
self.assertIs(new_pink.default, models.NOT_PROVIDED)
self.assertEqual(new_pink.db_default, Value(4))
pony = project_state.apps.get_model(app_label, "pony").objects.create(weight=1)
self.assertEqual(pony.pink, 3)
# Alter field.
with connection.schema_editor() as editor:
operation.database_forwards(app_label, editor, project_state, new_state)
pony = new_state.apps.get_model(app_label, "pony").objects.create(weight=1)
if not connection.features.can_return_columns_from_insert:
pony.refresh_from_db()
self.assertEqual(pony.pink, 4)
# Reversal.
with connection.schema_editor() as editor:
operation.database_backwards(app_label, editor, new_state, project_state)
pony = project_state.apps.get_model(app_label, "pony").objects.create(weight=1)
self.assertEqual(pony.pink, 3)
def test_alter_field_change_nullable_to_database_default_not_null(self):
"""
The AlterField operation changing a null field to db_default.
"""
app_label = "test_alflcntddnn"
project_state = self.set_up_test_model(app_label)
operation = migrations.AlterField(
"Pony", "green", models.IntegerField(db_default=4)
)
new_state = project_state.clone()
operation.state_forwards(app_label, new_state)
old_green = project_state.models[app_label, "pony"].fields["green"]
self.assertIs(old_green.db_default, models.NOT_PROVIDED)
new_green = new_state.models[app_label, "pony"].fields["green"]
self.assertEqual(new_green.db_default, Value(4))
old_pony = project_state.apps.get_model(app_label, "pony").objects.create(
weight=1
)
self.assertIsNone(old_pony.green)
# Alter field.
with connection.schema_editor() as editor:
operation.database_forwards(app_label, editor, project_state, new_state)
old_pony.refresh_from_db()
self.assertEqual(old_pony.green, 4)
pony = new_state.apps.get_model(app_label, "pony").objects.create(weight=1)
if not connection.features.can_return_columns_from_insert:
pony.refresh_from_db()
self.assertEqual(pony.green, 4)
# Reversal.
with connection.schema_editor() as editor:
operation.database_backwards(app_label, editor, new_state, project_state)
pony = project_state.apps.get_model(app_label, "pony").objects.create(weight=1)
self.assertIsNone(pony.green)
@skipIfDBFeature("interprets_empty_strings_as_nulls")
def test_alter_field_change_blank_nullable_database_default_to_not_null(self):
app_label = "test_alflcbnddnn"
table_name = f"{app_label}_pony"
project_state = self.set_up_test_model(app_label)
default = "Yellow"
operation = migrations.AlterField(
"Pony",
"yellow",
models.CharField(blank=True, db_default=default, max_length=20),
)
new_state = project_state.clone()
operation.state_forwards(app_label, new_state)
self.assertColumnNull(table_name, "yellow")
pony = project_state.apps.get_model(app_label, "pony").objects.create(
weight=1, yellow=None
)
self.assertIsNone(pony.yellow)
# Alter field.
with connection.schema_editor() as editor:
operation.database_forwards(app_label, editor, project_state, new_state)
self.assertColumnNotNull(table_name, "yellow")
pony.refresh_from_db()
self.assertEqual(pony.yellow, default)
pony = new_state.apps.get_model(app_label, "pony").objects.create(weight=1)
if not connection.features.can_return_columns_from_insert:
pony.refresh_from_db()
self.assertEqual(pony.yellow, default)
# Reversal.
with connection.schema_editor() as editor:
operation.database_backwards(app_label, editor, new_state, project_state)
self.assertColumnNull(table_name, "yellow")
pony = project_state.apps.get_model(app_label, "pony").objects.create(
weight=1, yellow=None
)
self.assertIsNone(pony.yellow)
def test_alter_field_add_db_column_noop(self):
"""
AlterField operation is a noop when adding only a db_column and the

27
tests/schema/tests.py
View File

@ -2102,6 +2102,33 @@ class SchemaTests(TransactionTestCase):
with self.assertRaises(IntegrityError):
NoteRename.objects.create(detail_info=None)
@isolate_apps("schema")
def test_rename_keep_db_default(self):
"""Renaming a field shouldn't affect a database default."""
class AuthorDbDefault(Model):
birth_year = IntegerField(db_default=1985)
class Meta:
app_label = "schema"
self.isolated_local_models = [AuthorDbDefault]
with connection.schema_editor() as editor:
editor.create_model(AuthorDbDefault)
columns = self.column_classes(AuthorDbDefault)
self.assertEqual(columns["birth_year"][1].default, "1985")
old_field = AuthorDbDefault._meta.get_field("birth_year")
new_field = IntegerField(db_default=1985)
new_field.set_attributes_from_name("renamed_year")
new_field.model = AuthorDbDefault
with connection.schema_editor(
atomic=connection.features.supports_atomic_references_rename
) as editor:
editor.alter_field(AuthorDbDefault, old_field, new_field, strict=True)
columns = self.column_classes(AuthorDbDefault)
self.assertEqual(columns["renamed_year"][1].default, "1985")
@skipUnlessDBFeature(
"supports_column_check_constraints", "can_introspect_check_constraints"
)