id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
30883	select_for_update doesn't include submodels in PostgreSQL	Abhijeet Viswa	nobody	"Consider the following line of code: 


{{{
order = Order.objects.filter(uuid=order_uuid).prefetch_related(
            Prefetch(
                lookup='items',
                queryset=items
            )
        ).select_related('outlet').select_related('user').select_related('outlet__group') \
         .select_for_update(of=('self', 'outlet'))
}}}

Here, `outlet` is a relation defined as: 
{{{
outlet = models.ForeignKey(Outlet, on_delete=models.PROTECT, related_name=""orders"")
}}}

Here the `Order` and `Outlet` models are sub-models to `Transaction` and `Shop` models respectively (which are situated in another Django app)
The former models reside in an app called `cashless` while the latter reside in `payment_gateway`.

I logged the PSQL output and this is the resultant query for the above line of code:
{{{
SELECT 
""payment_gateway_transaction"".""uuid"", 
""payment_gateway_transaction"".""ref_number"", 
""payment_gateway_transaction"".""shop_id"", 
""payment_gateway_transaction"".""user_id"", 
""payment_gateway_transaction"".""timestamp"", 
""payment_gateway_transaction"".""amount"", 
""payment_gateway_transaction"".""payment_method"", 
""payment_gateway_transaction"".""transaction_status"", 
""payment_gateway_transaction"".""service"", 
""cashless_order"".""transaction_ptr_id"", ""cashless_order"".""token"", 
""cashless_order"".""outlet_id"", ""cashless_order"".""order_status"", 
""cashless_order"".""order_start_time"", ""cashless_order"".""order_end_time"", 
""cashless_order"".""order_collect_time"", ""cashless_order"".""order_review"", 
""cashless_order"".""order_ratings"", ""authentication_user"".""id"", 
""authentication_user"".""password"", ""authentication_user"".""last_login"", 
""authentication_user"".""is_superuser"", ""authentication_user"".""email"", 
""authentication_user"".""student_id"", ""authentication_user"".""first_name"", 
""authentication_user"".""last_name"", ""authentication_user"".""date_joined"", 
""authentication_user"".""ip_address"", ""authentication_user"".""mac_address"", 
""authentication_user"".""location"", ""authentication_user"".""phone_number"", 
""authentication_user"".""total_spent"", ""authentication_user"".""is_banned"", 
""authentication_user"".""needs_student_id"", 
""authentication_user"".""generated_at"", ""authentication_user"".""verify_token"", 
""authentication_user"".""is_active"", ""payment_gateway_shop"".""uuid"", 
""payment_gateway_shop"".""name"", ""payment_gateway_shop"".""location_id"", 
""payment_gateway_shop"".""location_coords"", 
""payment_gateway_shop"".""tax_applicable"", 
""payment_gateway_shop"".""percentage_tax"", 
""payment_gateway_shop"".""gst_number"", ""payment_gateway_shop"".""open"", 
""payment_gateway_shop"".""active"", ""payment_gateway_shop"".""group_id"", 
""cashless_outlet"".""shop_ptr_id"", ""cashless_outlet"".""start_time"", 
""cashless_outlet"".""end_time"", ""cashless_outlet"".""break_start_time"", 
""cashless_outlet"".""break_end_time"", ""cashless_outlet"".""items_limit"", 
""cashless_outlet"".""image"", ""cashless_outlet"".""description"", 
""cashless_outlet"".""on_cashless"", ""cashless_outlet"".""ratings"", 
""cashless_outlet"".""latest_token"", ""auth_group"".""id"", ""auth_group"".""name"" 
FROM ""cashless_order"" 
INNER JOIN ""payment_gateway_transaction"" ON  (""cashless_order"".""transaction_ptr_id"" =  ""payment_gateway_transaction"".""uuid"") 
INNER JOIN ""authentication_user"" ON (""payment_gateway_transaction"".""user_id"" = ""authentication_user"".""id"") 
INNER JOIN ""cashless_outlet"" ON (""cashless_order"".""outlet_id"" = ""cashless_outlet"".""shop_ptr_id"") 
INNER JOIN ""payment_gateway_shop"" ON (""cashless_outlet"".""shop_ptr_id"" = ""payment_gateway_shop"".""uuid"") 
INNER JOIN ""auth_group"" ON (""payment_gateway_shop"".""group_id"" = ""auth_group"".""id"") 
WHERE ""cashless_order"".""transaction_ptr_id"" = '6e413b2e8f07-4452-8cd2-5bc186e7ffcb'::uuid 
FOR UPDATE OF ""payment_gateway_transaction"", ""payment_gateway_shop""
}}}

As seen from the SQL query, only the rows of tables `payment_gateway_transaction` and `payment_gateway_model` (`Transaction` and `Shop` models respectively) are being locked for update. This is despite the fact that the original Queryset references `Order` (a submodel of `Transaction`). 

Since the of parameter provides no way of specifying the Models/tables that we would want to lock, there is no way around this problem. 
"	Bug	closed	Database layer (models, ORM)	2.2	Normal	invalid	psql, select_for_update, transactions		Unreviewed	0	0	0	0	0	0