Python django.db.router.db_for_read() Examples

def validate(self, value, model_instance):
        if self.rel.parent_link:
            return
        super(ForeignKey, self).validate(value, model_instance)
        if value is None:
            return

        using = router.db_for_read(model_instance.__class__, instance=model_instance)
        qs = self.rel.to._default_manager.using(using).filter(
            **{self.rel.field_name: value}
        )
        qs = qs.complex_filter(self.get_limit_choices_to())
        if not qs.exists():
            raise exceptions.ValidationError(
                self.error_messages['invalid'],
                code='invalid',
                params={
                    'model': self.rel.to._meta.verbose_name, 'pk': value,
                    'field': self.rel.field_name, 'value': value,
                },  # 'pk' is included for backwards compatibility
            ) 

def has_key(self, key, version=None):
        key = self.make_key(key, version=version)
        self.validate_key(key)

        db = router.db_for_read(self.cache_model_class)
        table = connections[db].ops.quote_name(self._table)

        if settings.USE_TZ:
            now = datetime.utcnow()
        else:
            now = datetime.now()
        now = now.replace(microsecond=0)

        with connections[db].cursor() as cursor:
            cursor.execute("SELECT cache_key FROM %s "
                           "WHERE cache_key = %%s and expires > %%s" % table,
                           [key, connections[db].ops.value_to_db_datetime(now)])
            return cursor.fetchone() is not None 

def validate(self, value, model_instance):
        if self.remote_field.parent_link:
            return
        super(ForeignKey, self).validate(value, model_instance)
        if value is None:
            return

        using = router.db_for_read(self.remote_field.model, instance=model_instance)
        qs = self.remote_field.model._default_manager.using(using).filter(
            **{self.remote_field.field_name: value}
        )
        qs = qs.complex_filter(self.get_limit_choices_to())
        if not qs.exists():
            raise exceptions.ValidationError(
                self.error_messages['invalid'],
                code='invalid',
                params={
                    'model': self.remote_field.model._meta.verbose_name, 'pk': value,
                    'field': self.remote_field.field_name, 'value': value,
                },  # 'pk' is included for backwards compatibility
            ) 

def validate(self, value, model_instance):
        if self.remote_field.parent_link:
            return
        super().validate(value, model_instance)
        if value is None:
            return

        using = router.db_for_read(self.remote_field.model, instance=model_instance)
        qs = self.remote_field.model._default_manager.using(using).filter(
            **{self.remote_field.field_name: value}
        )
        qs = qs.complex_filter(self.get_limit_choices_to())
        if not qs.exists():
            raise exceptions.ValidationError(
                self.error_messages['invalid'],
                code='invalid',
                params={
                    'model': self.remote_field.model._meta.verbose_name, 'pk': value,
                    'field': self.remote_field.field_name, 'value': value,
                },  # 'pk' is included for backwards compatibility
            ) 

def validate(self, value, model_instance):
        if self.remote_field.parent_link:
            return
        super().validate(value, model_instance)
        if value is None:
            return

        using = router.db_for_read(self.remote_field.model, instance=model_instance)
        qs = self.remote_field.model._default_manager.using(using).filter(
            **{self.remote_field.field_name: value}
        )
        qs = qs.complex_filter(self.get_limit_choices_to())
        if not qs.exists():
            raise exceptions.ValidationError(
                self.error_messages['invalid'],
                code='invalid',
                params={
                    'model': self.remote_field.model._meta.verbose_name, 'pk': value,
                    'field': self.remote_field.field_name, 'value': value,
                },  # 'pk' is included for backwards compatibility
            ) 

def get_many(self, keys, version=None):
        made_key_to_key = {self.make_key(key, version=version): key for key in keys}
        made_keys = list(made_key_to_key.keys())
        for key in made_keys:
            self.validate_key(key)

        db = router.db_for_read(self.cache_model_class)
        table = connections[db].ops.quote_name(self._table)

        with connections[db].cursor() as cursor:
            cursor.execute(
                self._get_many_query.format(
                    table=table, list_sql=get_list_sql(made_keys)
                ),
                made_keys + [self._now()],
            )
            rows = cursor.fetchall()

        data = {}

        for made_key, value, value_type in rows:
            key = made_key_to_key[made_key]
            data[key] = self.decode(value, value_type)

        return data 

def validate(self, value, model_instance):
        if self.remote_field.parent_link:
            return
        super(ForeignKey, self).validate(value, model_instance)
        if value is None:
            return

        using = router.db_for_read(self.remote_field.model, instance=model_instance)
        qs = self.remote_field.model._default_manager.using(using).filter(
            **{self.remote_field.field_name: value}
        )
        qs = qs.complex_filter(self.get_limit_choices_to())
        if not qs.exists():
            raise exceptions.ValidationError(
                self.error_messages['invalid'],
                code='invalid',
                params={
                    'model': self.remote_field.model._meta.verbose_name, 'pk': value,
                    'field': self.remote_field.field_name, 'value': value,
                },  # 'pk' is included for backwards compatibility
            ) 

def validate(self, value, model_instance):
        if self.remote_field.parent_link:
            return
        super(ForeignKey, self).validate(value, model_instance)
        if value is None:
            return

        using = router.db_for_read(model_instance.__class__, instance=model_instance)
        qs = self.remote_field.model._default_manager.using(using).filter(
            **{self.remote_field.field_name: value}
        )
        qs = qs.complex_filter(self.get_limit_choices_to())
        if not qs.exists():
            raise exceptions.ValidationError(
                self.error_messages['invalid'],
                code='invalid',
                params={
                    'model': self.remote_field.model._meta.verbose_name, 'pk': value,
                    'field': self.remote_field.field_name, 'value': value,
                },  # 'pk' is included for backwards compatibility
            ) 

def has_key(self, key, version=None):
        key = self.make_key(key, version=version)
        self.validate_key(key)

        db = router.db_for_read(self.cache_model_class)
        table = connections[db].ops.quote_name(self._table)
        cursor = connections[db].cursor()

        if settings.USE_TZ:
            now = datetime.utcnow()
        else:
            now = datetime.now()
        now = now.replace(microsecond=0)
        cursor.execute("SELECT cache_key FROM %s "
                       "WHERE cache_key = %%s and expires > %%s" % table,
                       [key, connections[db].ops.value_to_db_datetime(now)])
        return cursor.fetchone() is not None 

def get(self, key, default=None, version=None):
        key = self.make_key(key, version=version)
        self.validate_key(key)
        db = router.db_for_read(self.cache_model_class)
        table = connections[db].ops.quote_name(self._table)
        cursor = connections[db].cursor()

        cursor.execute("SELECT cache_key, value, expires FROM %s "
                       "WHERE cache_key = %%s" % table, [key])
        row = cursor.fetchone()
        if row is None:
            return default
        now = timezone.now()
        if row[2] < now:
            db = router.db_for_write(self.cache_model_class)
            cursor = connections[db].cursor()
            cursor.execute("DELETE FROM %s "
                           "WHERE cache_key = %%s" % table, [key])
            transaction.commit_unless_managed(using=db)
            return default
        value = connections[db].ops.process_clob(row[1])
        return pickle.loads(base64.b64decode(force_bytes(value))) 

def db(self):
        return self._db or router.db_for_read(self.model, **self._hints)

    #######################
    # PROXIES TO QUERYSET #
    ####################### 

def db_for_read(self, model, **hints):
        raise AttributeError 

def test_foreign_key_validation(self):
        "ForeignKey.validate() uses the correct database"
        mickey = Person.objects.using('other').create(name="Mickey")
        pluto = Pet.objects.using('other').create(name="Pluto", owner=mickey)
        self.assertIsNone(pluto.full_clean())

    # Any router that accesses `model` in db_for_read() works here. 

def test_foreign_key_validation_with_router(self):
        """
        ForeignKey.validate() passes `model` to db_for_read() even if
        model_instance=None.
        """
        if django.VERSION < (1, 11, 0):
            self.skipTest("TODO fix AttributeError: type object 'NoneType' has no attribute '_meta'")
        mickey = Person.objects.create(name="Mickey")
        owner_field = Pet._meta.get_field('owner')
        self.assertEqual(owner_field.clean(mickey.pk, None), mickey.pk) 

def test_partial_router(self):
        "A router can choose to implement a subset of methods"
        dive = Book.objects.using('other').create(title="Dive into Python",
                                                  published=datetime.date(2009, 5, 4))

        # First check the baseline behavior.

        self.assertEqual(router.db_for_read(User), 'other')
        self.assertEqual(router.db_for_read(Book), 'other')

        self.assertEqual(router.db_for_write(User), 'default')
        self.assertEqual(router.db_for_write(Book), 'default')

        self.assertTrue(router.allow_relation(dive, dive))

        self.assertTrue(router.allow_migrate_model('default', User))
        self.assertTrue(router.allow_migrate_model('default', Book))

        with override_settings(DATABASE_ROUTERS=[WriteRouter(), AuthRouter(), TestRouter()]):
            self.assertEqual(router.db_for_read(User), 'default')
            self.assertEqual(router.db_for_read(Book), 'other')

            self.assertEqual(router.db_for_write(User), 'writer')
            self.assertEqual(router.db_for_write(Book), 'writer')

            self.assertTrue(router.allow_relation(dive, dive))

            self.assertFalse(router.allow_migrate_model('default', User))
            self.assertTrue(router.allow_migrate_model('default', Book)) 

def db_for_read(self, model, **hints):
        raise AttributeError 

def test_refresh_router_instance_hint(self):
        router = Mock()
        router.db_for_read.return_value = None
        book = Book.objects.create(title='Dive Into Python', published=datetime.date(1957, 10, 12))
        with self.settings(DATABASE_ROUTERS=[router]):
            book.refresh_from_db()
        router.db_for_read.assert_called_once_with(Book, instance=book) 

def test_foreign_key_validation(self):
        "ForeignKey.validate() uses the correct database"
        mickey = Person.objects.using('other').create(name="Mickey")
        pluto = Pet.objects.using('other').create(name="Pluto", owner=mickey)
        self.assertIsNone(pluto.full_clean())

    # Any router that accesses `model` in db_for_read() works here. 

def test_foreign_key_validation_with_router(self):
        """
        ForeignKey.validate() passes `model` to db_for_read() even if
        model_instance=None.
        """
        mickey = Person.objects.create(name="Mickey")
        owner_field = Pet._meta.get_field('owner')
        self.assertEqual(owner_field.clean(mickey.pk, None), mickey.pk) 

def test_partial_router(self):
        "A router can choose to implement a subset of methods"
        dive = Book.objects.using('other').create(title="Dive into Python",
                                                  published=datetime.date(2009, 5, 4))

        # First check the baseline behavior.

        self.assertEqual(router.db_for_read(User), 'other')
        self.assertEqual(router.db_for_read(Book), 'other')

        self.assertEqual(router.db_for_write(User), 'default')
        self.assertEqual(router.db_for_write(Book), 'default')

        self.assertTrue(router.allow_relation(dive, dive))

        self.assertTrue(router.allow_migrate_model('default', User))
        self.assertTrue(router.allow_migrate_model('default', Book))

        with override_settings(DATABASE_ROUTERS=[WriteRouter(), AuthRouter(), TestRouter()]):
            self.assertEqual(router.db_for_read(User), 'default')
            self.assertEqual(router.db_for_read(Book), 'other')

            self.assertEqual(router.db_for_write(User), 'writer')
            self.assertEqual(router.db_for_write(Book), 'writer')

            self.assertTrue(router.allow_relation(dive, dive))

            self.assertFalse(router.allow_migrate_model('default', User))
            self.assertTrue(router.allow_migrate_model('default', Book)) 

def db_for_read(self, model, **hints):
        raise AttributeError 

def test_foreign_key_validation(self):
        "ForeignKey.validate() uses the correct database"
        mickey = Person.objects.using('other').create(name="Mickey")
        pluto = Pet.objects.using('other').create(name="Pluto", owner=mickey)
        self.assertIsNone(pluto.full_clean())

    # Any router that accesses `model` in db_for_read() works here. 

def test_foreign_key_validation_with_router(self):
        """
        ForeignKey.validate() passes `model` to db_for_read() even if
        model_instance=None.
        """
        mickey = Person.objects.create(name="Mickey")
        owner_field = Pet._meta.get_field('owner')
        self.assertEqual(owner_field.clean(mickey.pk, None), mickey.pk) 

def test_partial_router(self):
        "A router can choose to implement a subset of methods"
        dive = Book.objects.using('other').create(title="Dive into Python",
                                                  published=datetime.date(2009, 5, 4))

        # First check the baseline behavior.

        self.assertEqual(router.db_for_read(User), 'other')
        self.assertEqual(router.db_for_read(Book), 'other')

        self.assertEqual(router.db_for_write(User), 'default')
        self.assertEqual(router.db_for_write(Book), 'default')

        self.assertTrue(router.allow_relation(dive, dive))

        self.assertTrue(router.allow_migrate_model('default', User))
        self.assertTrue(router.allow_migrate_model('default', Book))

        with override_settings(DATABASE_ROUTERS=[WriteRouter(), AuthRouter(), TestRouter()]):
            self.assertEqual(router.db_for_read(User), 'default')
            self.assertEqual(router.db_for_read(Book), 'other')

            self.assertEqual(router.db_for_write(User), 'writer')
            self.assertEqual(router.db_for_write(Book), 'writer')

            self.assertTrue(router.allow_relation(dive, dive))

            self.assertFalse(router.allow_migrate_model('default', User))
            self.assertTrue(router.allow_migrate_model('default', Book)) 

def db(self):
        return self._db or router.db_for_read(self.model, **self._hints)

    #######################
    # PROXIES TO QUERYSET #
    ####################### 

def get_with_prefix(self, prefix, version=None):
        if self.reverse_key_func is None:
            raise ValueError(
                "To use the _with_prefix commands with a custom KEY_FUNCTION, "
                "you need to specify a custom REVERSE_KEY_FUNCTION too."
            )

        if version is None:
            version = self.version

        db = router.db_for_read(self.cache_model_class)
        table = connections[db].ops.quote_name(self._table)

        prefix = self.make_key(prefix + "%", version=version)
        version = str(version)

        with connections[db].cursor() as cursor:
            cursor.execute(
                """SELECT cache_key, value, value_type
                   FROM {table}
                   WHERE cache_key LIKE %s AND
                         expires >= %s""".format(
                    table=table
                ),
                (prefix, self._now()),
            )
            rows = cursor.fetchall()

            data = {}
            for made_key, value, value_type in rows:
                key, key_prefix, key_version = self.reverse_key_func(made_key)
                data[key] = self.decode(value, value_type)

            return data 

def keys_with_prefix(self, prefix, version=None):
        if self.reverse_key_func is None:
            raise ValueError(
                "To use the _with_prefix commands with a custom KEY_FUNCTION, "
                "you need to specify a custom REVERSE_KEY_FUNCTION too."
            )

        if version is None:
            version = self.version

        db = router.db_for_read(self.cache_model_class)
        table = connections[db].ops.quote_name(self._table)

        prefix = self.make_key(prefix + "%", version=version)

        with connections[db].cursor() as cursor:
            cursor.execute(
                """SELECT cache_key FROM {table}
                   WHERE cache_key LIKE %s AND
                         expires >= %s""".format(
                    table=table
                ),
                (prefix, self._now()),
            )
            rows = cursor.fetchall()
            full_keys = {row[0] for row in rows}

            keys = {}
            for full_key in full_keys:
                key, key_prefix, key_version = self.reverse_key_func(full_key)

                if key_version == version:
                    keys[key] = key_version
            return set(keys.keys()) 

def has_key(self, key, version=None):
        key = self.make_key(key, version=version)
        self.validate_key(key)

        db = router.db_for_read(self.cache_model_class)
        table = connections[db].ops.quote_name(self._table)

        with connections[db].cursor() as cursor:
            cursor.execute(self._has_key_query.format(table=table), (key, self._now()))
            return cursor.fetchone() is not None 

def get(self, key, default=None, version=None):
        key = self.make_key(key, version=version)
        self.validate_key(key)
        db = router.db_for_read(self.cache_model_class)
        table = connections[db].ops.quote_name(self._table)

        with connections[db].cursor() as cursor:
            cursor.execute(self._get_query.format(table=table), (key, self._now()))
            row = cursor.fetchone()

        if row is None:
            return default
        else:
            value, value_type = row
            return self.decode(value, value_type) 

def db(self):
        return self._db or router.db_for_read(self.model, **self._hints)

    #######################
    # PROXIES TO QUERYSET #
    #######################