diff options
Diffstat (limited to 'django/db/models/expressions.py')
| -rw-r--r-- | django/db/models/expressions.py | 37 |
1 files changed, 37 insertions, 0 deletions
diff --git a/django/db/models/expressions.py b/django/db/models/expressions.py index d412e7657e..e1861759c4 100644 --- a/django/db/models/expressions.py +++ b/django/db/models/expressions.py @@ -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): """ |