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  • Documentation version: 2.2

Source code for django.db.models.constraints

from django.db.models.query_utils import Q
from django.db.models.sql.query import Query

__all__ = ['CheckConstraint', 'UniqueConstraint']


class BaseConstraint:
    def __init__(self, name):
        self.name = name

    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.')

    def deconstruct(self):
        path = '%s.%s' % (self.__class__.__module__, self.__class__.__name__)
        path = path.replace('django.db.models.constraints', 'django.db.models')
        return (path, (), {'name': self.name})

    def clone(self):
        _, args, kwargs = self.deconstruct()
        return self.__class__(*args, **kwargs)


[docs]class CheckConstraint(BaseConstraint): def __init__(self, *, check, name): self.check = check super().__init__(name) def _get_check_sql(self, model, schema_editor): query = Query(model=model) 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 __repr__(self): return "<%s: check='%s' name=%r>" % (self.__class__.__name__, self.check, self.name) def __eq__(self, other): return ( isinstance(other, CheckConstraint) and self.name == other.name and self.check == other.check ) def deconstruct(self): path, args, kwargs = super().deconstruct() kwargs['check'] = self.check return path, args, kwargs
[docs]class UniqueConstraint(BaseConstraint): def __init__(self, *, fields, name, condition=None): if not fields: raise ValueError('At least one field is required to define a unique constraint.') if not isinstance(condition, (type(None), Q)): raise ValueError('UniqueConstraint.condition must be a Q instance.') self.fields = tuple(fields) self.condition = condition super().__init__(name) def _get_condition_sql(self, model, schema_editor): if self.condition is None: return None query = Query(model=model) 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 constraint_sql(self, model, schema_editor): fields = [model._meta.get_field(field_name).column for field_name in self.fields] condition = self._get_condition_sql(model, schema_editor) return schema_editor._unique_sql(model, fields, self.name, condition=condition) def create_sql(self, model, schema_editor): fields = [model._meta.get_field(field_name).column for field_name in self.fields] condition = self._get_condition_sql(model, schema_editor) return schema_editor._create_unique_sql(model, fields, self.name, condition=condition) def remove_sql(self, model, schema_editor): condition = self._get_condition_sql(model, schema_editor) return schema_editor._delete_unique_sql(model, self.name, condition=condition) def __repr__(self): return '<%s: fields=%r name=%r%s>' % ( self.__class__.__name__, self.fields, self.name, '' if self.condition is None else ' condition=%s' % self.condition, ) def __eq__(self, other): return ( isinstance(other, UniqueConstraint) and self.name == other.name and self.fields == other.fields and self.condition == other.condition ) def deconstruct(self): path, args, kwargs = super().deconstruct() kwargs['fields'] = self.fields if self.condition: kwargs['condition'] = self.condition return path, args, kwargs
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