How to have edges/totalCount on a relationship field?

[rok-povsic]

Hey,

I'd like to have edges/node/totalCount support on a relationship field.

E.g. if looking at the flask_alchemy example app, I'd like to have query such as this (changes are in bold):

{
  allEmployees {
    edges {
      node {
        id,
        name,
        department {
          totalCount
          edges {
              id,
              name
           }
        },
        role {
          totalCount
          edges {
            id,
            name
           }
        }
      }
    }
  }
}

Can this be done?

Thank you

[shanmugh]

+1

[shanmugh]

Also, I tried the work-around suggested here - graphql-python/graphene#151 by using https://pypi.python.org/pypi/graphene-sqlalchemy/2.0.dev2017072601 but the Connection object appears to be missing the length field.

I had to fork from graphene-sqlalchemy-1.1.1 and add this patch (d66aa07) to get it working.

[singingwolfboy]

@shanmugh, can you make a pull request to add your modification to graphene-sqlalchemy? Or post a working example, so that someone else can do so? I'd be happy to make that pull request for you, if you'd like.

[nmrtv]

@singingwolfboy, that modification (length) is already added, but if you need totalCount in your connection, you must inherit Connection class. Because totalCount is not in relay specification and not everyone needs it.

[singingwolfboy]

@neriusmika Can you show me how to do that? This is the code I have so far, and it doesn't seem to work...

import graphene
from graphene.relay import Node
from graphene_sqlalchemy import SQLAlchemyObjectType, SQLAlchemyConnectionField
from myapp import models


class CountableConnection(SQLAlchemyConnectionField):
    total_count = graphene.Int()

    def resolve_total_count(self, info):
        return self.length


class Contact(SQLAlchemyObjectType, interfaces=[Node]):
    class Meta:
        model = models.Contact


class User(SQLAlchemyObjectType, interfaces=[Node]):
    class Meta:
        model = models.User
        
    contacts = CountableConnection(Contact)

[nmrtv]

You need to inherit CountableConnection from graphene.relay.Connection, not from SQLAlchemyConnectionField. But there is a problem to pass that connection to your Contact class. It has connection parameter, but now it's useless, because Connection class needs node parameter and you will have circular reference. Probably the simplest way would be to reassign graphene.relay.Connection (look at #65 (comment)), but then it will be used in all your connections. The other way (which I prefer) is to change SQLAlchemyObjectType implementation.

[singingwolfboy]

@neriusmika That's helpful, but do you think you could provide an actual code example? I find it's easier to refer to an example, and tweak it from there.

[nmrtv]

Based on your example, you can try this code, but I did not check it:

import graphene
from graphene.relay import Node
from graphene_sqlalchemy import SQLAlchemyObjectType, SQLAlchemyConnectionField
from myapp import models


class CountableConnection(graphene.relay.Connection):
    class Meta:
        abstract = True

    total_count = graphene.Int()

    @staticmethod
    def resolve_total_count(root, info):
        return root.length

graphene.relay.Connection = CountableConnection


class Contact(SQLAlchemyObjectType, interfaces=[Node]):
    class Meta:
        model = models.Contact


class User(SQLAlchemyObjectType, interfaces=[Node]):
    class Meta:
        model = models.User
        

class Query(graphene.ObjectType):
    node = Node.Field()

    all_users = SQLAlchemyConnectionField(User)

[singingwolfboy]

That seems to work. Thank you for the help!

[sebastiandev]

Im looking for the same, but this approach is not working for me.
The relay.Connection is not been replaced, is still the base Connection. How can I specify that I want to use another Connection class?

I ended up subclassing SQLAlchemyObjectType to force it to use the CountableConnecition, like this:

class CountableConnection(graphene.relay.Connection):
    class Meta:
        abstract = True

    total_count = graphene.Int()

    @staticmethod
    def resolve_total_count(root, info, *args, **kwargs):
        return root.length


class CustomSQLAlchemyObjectType(SQLAlchemyObjectType):

    class Meta:
        abstract = True

    @classmethod
    def __init_subclass_with_meta__(cls, model=None, registry=None, skip_registry=False,
                                    only_fields=(), exclude_fields=(), connection=None,
                                    use_connection=None, interfaces=(), id=None, **options):
        # Force it to use the countable connection
        countable_conn = connection or CountableConnection.create_type(
            "{}CountableConnection".format(model.__name__),
            node=cls)

        super(CustomSQLAlchemyObjectType, cls).__init_subclass_with_meta__(
            model, 
            registry, 
            skip_registry,
            only_fields,
            exclude_fields, 
            countable_conn,
            use_connection, 
            interfaces, 
            id,
            **options)

Thanks

[CaselIT]

I've added a PR to fix this issue here #104