Django QuerySet: Format query result as custom dictionary - django

Question

I am working on a RBAC system for my Django-React app. I have this certain object structure that I want to generate but I am not sure how to do so directly from Django's QuerySet API.
Currently, I have this query
permissions |= PermissionAssignment.objects.filter(role=role['role__id']).values(
'permission__object__id',
'permission__object__name',
'permission__operation__id',
'permission__operation__name'
)
which returns this object on my frontend:
permissions: [
{
permission__object__id: 1,
permission__object__name: 'Post',
permission__operation__id: 1,
permission__operation__name: 'Read'
},
{
permission__object__id: 1,
permission__object__name: 'Post',
permission__operation__id: 2,
permission__operation__name: 'Write'
},
{
permission__object__id: 2,
permission__object__name: 'Event',
permission__operation__id: 2,
permission__operation__name: 'Read'
},
]
I do not require the permission object to have that complex structure. I only need to take hold of the object name and the operations enabled to this object for the current user. So basically, I just need it to be structured as:
permissions:[
"Post": {
operations: ['Read', 'Write']
},
"Event": {
operations: ['Read']
}
]
I know I can manipulate the original result on my frontend to get what I want, but I don't see that is necessary when I can format the result on the server-side level right away, except that I am not sure how to do that in Django.

Answer 1

You might be able to use list comprehension to achieve the desired outcome.
# NOTE: we use prefetch_related to avoid extra queries every time we access the object
permissions_qs = PermissionAssignment.objects.filter(role=role['role__id']).prefetch_related('object', 'operation')
d = {}
[d.update({p.object.name: {'operations': [p.operation.name]}}) if p.object.name not in d else d[p.object.name]['operations'].append(p.operations.name) for p in permissions_qs]

Answer 2

I have figured out the solution for what I wanted... The structure of the JSON response is different from what I defined in my question above, but I guess it is so much better.
However, I am posting the code here because I am having second thoughts with my approach i.e. I am starting to think the query is very expensive... and maybe someone can help check whether it is fine overall, or a bad practice indeed.
Code:
roles = RoleAssignment.objects.none()
modules = RoleModule.objects.none()
module_objects = ModuleObject.objects.none()
objects = Object.objects.none()
permissions = PermissionAssignment.objects.none()
roles = RoleAssignment.objects.filter(user=user).values('role__id', 'role__name')
for role in roles:
modules |= RoleModule.objects.filter(role=role['role__id']).values(
'role__id',
'module__id',
'module__name',
'module__slug',
'module__fontawesome_icon'
)
permissions |= PermissionAssignment.objects.filter(role=role['role__id']).values(
'permission__object__id',
'permission__object__name',
'permission__operation__id',
'permission__operation__name'
)
for module in modules:
module_objects |= ModuleObject.objects.filter(module=module['module__id']).values(
'module__id',
'module__name',
'object__id',
'object__name',
'object__slug'
)
# format modules to include respective objects and permissions
# this logic is primarily designed so that sidebar links can be...
# ...generated seamlessly thru frontend
formatted_modules = [
{
"name": x['module__name'],
"slug": x['module__slug'],
"icon": x['module__fontawesome_icon'],
"objects": [
{
"name": y['object__name'],
"slug": y['object__slug'],
"operations": [z['permission__operation__name'] for z in permissions if z['permission__object__id']==y['object__id']]
}
for y in module_objects if x['module__id']==y['module__id']
]
}
for x in modules
]
Then send it as response:
return Response({
"modules": formatted_modules
})
The JSON equivalence:
{
modules: [
{
name: 'Web Content',
slug: 'web-content',
icon: 'fas fa-newspaper',
objects: [
{
name: 'Post',
slug: 'post',
operations: [
'Read',
'Write',
'Modify',
'Delete'
]
}
]
},
{
name: 'Bids and Awards',
slug: 'bids-and-awards',
icon: 'fas fa-project-diagram',
objects: [
{
name: 'SRBP Goods & Services',
slug: 'srbp-goods-services',
operations: [
'Read',
'Write',
'Modify',
'Delete'
]
},
{
name: 'SRBP Infrastructure',
slug: 'srbp-infrastructure',
operations: [
'Read',
'Write',
'Modify',
'Delete'
]
}
]
}
]
}
In my UI: