Improved connection resolver from list

graphene/contrib/sqlalchemy/converter.py

@@ -19,16 +19,13 @@ def convert_sqlalchemy_relationship(relationship):
 
 
 def convert_sqlalchemy_column(column):
-    try:
-        return convert_sqlalchemy_type(column.type, column)
-    except Exception:
-        raise Exception(
-            "Don't know how to convert the SQLAlchemy field %s (%s)" % (column, column.__class__))
+    return convert_sqlalchemy_type(getattr(column, 'type', None), column)
 
 
 @singledispatch
 def convert_sqlalchemy_type(type, column):
-    raise Exception()
+    raise Exception(
+        "Don't know how to convert the SQLAlchemy field %s (%s)" % (column, column.__class__))
 
 
 @convert_sqlalchemy_type.register(types.Date)

graphene/contrib/sqlalchemy/fields.py

@@ -4,29 +4,25 @@ from ...core.types.base import FieldType
 from ...core.types.definitions import List
 from ...relay import ConnectionField
 from ...relay.utils import is_node
-from .utils import get_type_for_model
+from .utils import get_type_for_model, maybe_query, get_query
 
 
 class SQLAlchemyConnectionField(ConnectionField):
 
     def __init__(self, *args, **kwargs):
-        self.session = kwargs.pop('session', None)
         return super(SQLAlchemyConnectionField, self).__init__(*args, **kwargs)
 
     @property
     def model(self):
         return self.type._meta.model
 
-    def get_session(self, args, info):
-        return self.session
-
     def get_query(self, resolved_query, args, info):
-        self.get_session(args, info)
-        return resolved_query
+        return resolved_query or get_query(self.model, info)
 
     def from_list(self, connection_type, resolved, args, info):
-        qs = self.get_query(resolved, args, info)
-        return super(SQLAlchemyConnectionField, self).from_list(connection_type, qs, args, info)
+        query = self.get_query(resolved, args, info)
+        query = maybe_query(query)
+        return super(SQLAlchemyConnectionField, self).from_list(connection_type, query, args, info)
 
 
 class ConnectionOrListField(Field):

graphene/contrib/sqlalchemy/utils.py

@@ -1,8 +1,7 @@
 from sqlalchemy.ext.declarative.api import DeclarativeMeta
+from sqlalchemy.orm.query import Query
 
-
-# from sqlalchemy.orm.base import object_mapper
-# from sqlalchemy.orm.exc import UnmappedInstanceError
+from graphene.utils import LazyList
 
 
 def get_type_for_model(schema, model):
@@ -20,10 +19,27 @@ def get_session(info):
     return schema.options.get('session')
 
 
+def get_query(model, info):
+    query = getattr(model, 'query')
+    if not query:
+        query = get_session(info).query(model)
+    return query
+
+
+class WrappedQuery(LazyList):
+
+    def __len__(self):
+        # Dont calculate the length using len(query), as this will
+        # evaluate the whole queryset and return it's length.
+        # Use .count() instead
+        return self._origin.count()
+
+
+def maybe_query(value):
+    if isinstance(value, Query):
+        return WrappedQuery(value)
+    return value
+
+
 def is_mapped(obj):
     return isinstance(obj, DeclarativeMeta)
-    # try:
-    #     object_mapper(obj)
-    # except UnmappedInstanceError:
-    #     return False
-    # return True