from enum import Enum
from django.core.exceptions import FieldError, ValidationError
from django.db import connections
from django.db.models.expressions import Exists, ExpressionList, F, OrderBy
from django.db.models.indexes import IndexExpression
from django.db.models.lookups import Exact
from django.db.models.query_utils import Q
from django.db.models.sql.query import Query
from django.db.utils import DEFAULT_DB_ALIAS
from django.utils.translation import gettext_lazy as _
__all__ = ["BaseConstraint", "CheckConstraint", "Deferrable", "UniqueConstraint"]
[документация]class BaseConstraint:
default_violation_error_message = _("Constraint “%(name)s” is violated.")
violation_error_message = None
def __init__(self, name, violation_error_message=None):
self.name = name
if violation_error_message is not None:
self.violation_error_message = violation_error_message
else:
self.violation_error_message = self.default_violation_error_message
@property
def contains_expressions(self):
return False
def constraint_sql(self, model, schema_editor):
raise NotImplementedError("This method must be implemented by a subclass.")
def create_sql(self, model, schema_editor):
raise NotImplementedError("This method must be implemented by a subclass.")
def remove_sql(self, model, schema_editor):
raise NotImplementedError("This method must be implemented by a subclass.")
[документация] def validate(self, model, instance, exclude=None, using=DEFAULT_DB_ALIAS):
raise NotImplementedError("This method must be implemented by a subclass.")
def get_violation_error_message(self):
return self.violation_error_message % {"name": self.name}
def deconstruct(self):
path = "%s.%s" % (self.__class__.__module__, self.__class__.__name__)
path = path.replace("django.db.models.constraints", "django.db.models")
kwargs = {"name": self.name}
if (
self.violation_error_message is not None
and self.violation_error_message != self.default_violation_error_message
):
kwargs["violation_error_message"] = self.violation_error_message
return (path, (), kwargs)
def clone(self):
_, args, kwargs = self.deconstruct()
return self.__class__(*args, **kwargs)
[документация]class CheckConstraint(BaseConstraint):
def __init__(self, *, check, name, violation_error_message=None):
self.check = check
if not getattr(check, "conditional", False):
raise TypeError(
"CheckConstraint.check must be a Q instance or boolean expression."
)
super().__init__(name, violation_error_message=violation_error_message)
def _get_check_sql(self, model, schema_editor):
query = Query(model=model, alias_cols=False)
where = query.build_where(self.check)
compiler = query.get_compiler(connection=schema_editor.connection)
sql, params = where.as_sql(compiler, schema_editor.connection)
return sql % tuple(schema_editor.quote_value(p) for p in params)
def constraint_sql(self, model, schema_editor):
check = self._get_check_sql(model, schema_editor)
return schema_editor._check_sql(self.name, check)
def create_sql(self, model, schema_editor):
check = self._get_check_sql(model, schema_editor)
return schema_editor._create_check_sql(model, self.name, check)
def remove_sql(self, model, schema_editor):
return schema_editor._delete_check_sql(model, self.name)
def validate(self, model, instance, exclude=None, using=DEFAULT_DB_ALIAS):
against = instance._get_field_value_map(meta=model._meta, exclude=exclude)
try:
if not Q(self.check).check(against, using=using):
raise ValidationError(self.get_violation_error_message())
except FieldError:
pass
def __repr__(self):
return "<%s: check=%s name=%s>" % (
self.__class__.__qualname__,
self.check,
repr(self.name),
)
def __eq__(self, other):
if isinstance(other, CheckConstraint):
return (
self.name == other.name
and self.check == other.check
and self.violation_error_message == other.violation_error_message
)
return super().__eq__(other)
def deconstruct(self):
path, args, kwargs = super().deconstruct()
kwargs["check"] = self.check
return path, args, kwargs
class Deferrable(Enum):
DEFERRED = "deferred"
IMMEDIATE = "immediate"
# A similar format was proposed for Python 3.10.
def __repr__(self):
return f"{self.__class__.__qualname__}.{self._name_}"
[документация]class UniqueConstraint(BaseConstraint):
def __init__(
self,
*expressions,
fields=(),
name=None,
condition=None,
deferrable=None,
include=None,
opclasses=(),
violation_error_message=None,
):
if not name:
raise ValueError("A unique constraint must be named.")
if not expressions and not fields:
raise ValueError(
"At least one field or expression is required to define a "
"unique constraint."
)
if expressions and fields:
raise ValueError(
"UniqueConstraint.fields and expressions are mutually exclusive."
)
if not isinstance(condition, (type(None), Q)):
raise ValueError("UniqueConstraint.condition must be a Q instance.")
if condition and deferrable:
raise ValueError("UniqueConstraint with conditions cannot be deferred.")
if include and deferrable:
raise ValueError("UniqueConstraint with include fields cannot be deferred.")
if opclasses and deferrable:
raise ValueError("UniqueConstraint with opclasses cannot be deferred.")
if expressions and deferrable:
raise ValueError("UniqueConstraint with expressions cannot be deferred.")
if expressions and opclasses:
raise ValueError(
"UniqueConstraint.opclasses cannot be used with expressions. "
"Use django.contrib.postgres.indexes.OpClass() instead."
)
if not isinstance(deferrable, (type(None), Deferrable)):
raise ValueError(
"UniqueConstraint.deferrable must be a Deferrable instance."
)
if not isinstance(include, (type(None), list, tuple)):
raise ValueError("UniqueConstraint.include must be a list or tuple.")
if not isinstance(opclasses, (list, tuple)):
raise ValueError("UniqueConstraint.opclasses must be a list or tuple.")
if opclasses and len(fields) != len(opclasses):
raise ValueError(
"UniqueConstraint.fields and UniqueConstraint.opclasses must "
"have the same number of elements."
)
self.fields = tuple(fields)
self.condition = condition
self.deferrable = deferrable
self.include = tuple(include) if include else ()
self.opclasses = opclasses
self.expressions = tuple(
F(expression) if isinstance(expression, str) else expression
for expression in expressions
)
super().__init__(name, violation_error_message=violation_error_message)
@property
def contains_expressions(self):
return bool(self.expressions)
def _get_condition_sql(self, model, schema_editor):
if self.condition is None:
return None
query = Query(model=model, alias_cols=False)
where = query.build_where(self.condition)
compiler = query.get_compiler(connection=schema_editor.connection)
sql, params = where.as_sql(compiler, schema_editor.connection)
return sql % tuple(schema_editor.quote_value(p) for p in params)
def _get_index_expressions(self, model, schema_editor):
if not self.expressions:
return None
index_expressions = []
for expression in self.expressions:
index_expression = IndexExpression(expression)
index_expression.set_wrapper_classes(schema_editor.connection)
index_expressions.append(index_expression)
return ExpressionList(*index_expressions).resolve_expression(
Query(model, alias_cols=False),
)
def constraint_sql(self, model, schema_editor):
fields = [model._meta.get_field(field_name) for field_name in self.fields]
include = [
model._meta.get_field(field_name).column for field_name in self.include
]
condition = self._get_condition_sql(model, schema_editor)
expressions = self._get_index_expressions(model, schema_editor)
return schema_editor._unique_sql(
model,
fields,
self.name,
condition=condition,
deferrable=self.deferrable,
include=include,
opclasses=self.opclasses,
expressions=expressions,
)
def create_sql(self, model, schema_editor):
fields = [model._meta.get_field(field_name) for field_name in self.fields]
include = [
model._meta.get_field(field_name).column for field_name in self.include
]
condition = self._get_condition_sql(model, schema_editor)
expressions = self._get_index_expressions(model, schema_editor)
return schema_editor._create_unique_sql(
model,
fields,
self.name,
condition=condition,
deferrable=self.deferrable,
include=include,
opclasses=self.opclasses,
expressions=expressions,
)
def remove_sql(self, model, schema_editor):
condition = self._get_condition_sql(model, schema_editor)
include = [
model._meta.get_field(field_name).column for field_name in self.include
]
expressions = self._get_index_expressions(model, schema_editor)
return schema_editor._delete_unique_sql(
model,
self.name,
condition=condition,
deferrable=self.deferrable,
include=include,
opclasses=self.opclasses,
expressions=expressions,
)
def __repr__(self):
return "<%s:%s%s%s%s%s%s%s>" % (
self.__class__.__qualname__,
"" if not self.fields else " fields=%s" % repr(self.fields),
"" if not self.expressions else " expressions=%s" % repr(self.expressions),
" name=%s" % repr(self.name),
"" if self.condition is None else " condition=%s" % self.condition,
"" if self.deferrable is None else " deferrable=%r" % self.deferrable,
"" if not self.include else " include=%s" % repr(self.include),
"" if not self.opclasses else " opclasses=%s" % repr(self.opclasses),
)
def __eq__(self, other):
if isinstance(other, UniqueConstraint):
return (
self.name == other.name
and self.fields == other.fields
and self.condition == other.condition
and self.deferrable == other.deferrable
and self.include == other.include
and self.opclasses == other.opclasses
and self.expressions == other.expressions
and self.violation_error_message == other.violation_error_message
)
return super().__eq__(other)
def deconstruct(self):
path, args, kwargs = super().deconstruct()
if self.fields:
kwargs["fields"] = self.fields
if self.condition:
kwargs["condition"] = self.condition
if self.deferrable:
kwargs["deferrable"] = self.deferrable
if self.include:
kwargs["include"] = self.include
if self.opclasses:
kwargs["opclasses"] = self.opclasses
return path, self.expressions, kwargs
def validate(self, model, instance, exclude=None, using=DEFAULT_DB_ALIAS):
queryset = model._default_manager.using(using)
if self.fields:
lookup_kwargs = {}
for field_name in self.fields:
if exclude and field_name in exclude:
return
field = model._meta.get_field(field_name)
lookup_value = getattr(instance, field.attname)
if lookup_value is None or (
lookup_value == ""
and connections[using].features.interprets_empty_strings_as_nulls
):
# A composite constraint containing NULL value cannot cause
# a violation since NULL != NULL in SQL.
return
lookup_kwargs[field.name] = lookup_value
queryset = queryset.filter(**lookup_kwargs)
else:
# Ignore constraints with excluded fields.
if exclude:
for expression in self.expressions:
if hasattr(expression, "flatten"):
for expr in expression.flatten():
if isinstance(expr, F) and expr.name in exclude:
return
elif isinstance(expression, F) and expression.name in exclude:
return
replacements = {
F(field): value
for field, value in instance._get_field_value_map(
meta=model._meta, exclude=exclude
).items()
}
expressions = []
for expr in self.expressions:
# Ignore ordering.
if isinstance(expr, OrderBy):
expr = expr.expression
expressions.append(Exact(expr, expr.replace_expressions(replacements)))
queryset = queryset.filter(*expressions)
model_class_pk = instance._get_pk_val(model._meta)
if not instance._state.adding and model_class_pk is not None:
queryset = queryset.exclude(pk=model_class_pk)
if not self.condition:
if queryset.exists():
if self.expressions:
raise ValidationError(self.get_violation_error_message())
# When fields are defined, use the unique_error_message() for
# backward compatibility.
for model, constraints in instance.get_constraints():
for constraint in constraints:
if constraint is self:
raise ValidationError(
instance.unique_error_message(model, self.fields)
)
else:
against = instance._get_field_value_map(meta=model._meta, exclude=exclude)
try:
if (self.condition & Exists(queryset.filter(self.condition))).check(
against, using=using
):
raise ValidationError(self.get_violation_error_message())
except FieldError:
pass