def connection_resolver(cls, resolver, connection, model, root, info,
**args):
iterable = resolver(root, info, **args)
first = args.get('first')
last = args.get('last')
(_, after) = from_global_id(
args.get('after')) if args.get('after') else (None, None)
(_, before) = from_global_id(
args.get('before')) if args.get('before') else (None, None)
has_previous_page = bool(after)
page_size = first if first else last if last else None
# get a full scan query since we have no resolved iterable from relationship or resolver function
if not iterable and not root:
query = cls.get_query(model, info, **args)
iterable = query()
if first or last or after or before:
raise NotImplementedError(
"DynamoDB scan operations have no predictable sort. Arguments first, last, after "
+ "and before will have unpredictable results")
iterable = iterable if isinstance(
iterable, list) else list(iterable) if iterable else []
if last:
iterable = iterable[-last:]
(has_next,
edges) = cls.get_edges_from_iterable(iterable,
model,
info,
edge_type=connection.Edge,
after=after,
page_size=page_size)
key_name = get_key_name(model)
try:
start_cursor = getattr(edges[0].node, key_name)
end_cursor = getattr(edges[-1].node, key_name)
except IndexError:
start_cursor = None
end_cursor = None
optional_args = {}
total_count = len(iterable)
if 'total_count' in connection._meta.fields:
optional_args["total_count"] = total_count
# Construct the connection
return connection(
edges=edges,
page_info=PageInfo(
start_cursor=start_cursor if start_cursor else '',
end_cursor=end_cursor if end_cursor else '',
has_previous_page=has_previous_page,
has_next_page=has_next),
**optional_args)
def get_edges_from_iterable(cls,
iterable,
model,
info,
edge_type=Edge,
after=None,
page_size=None):
has_next = False
key_name = get_key_name(model)
after_index = 0
if after:
after_index = next(
(i for i, item in enumerate(iterable)
if str(getattr(item, key_name)) == after),
None,
)
if after_index is None:
return None
else:
after_index += 1
if page_size:
has_next = len(iterable) - after_index > page_size
iterable = iterable[after_index:after_index + page_size]
else:
iterable = iterable[after_index:]
# trigger a batch get to speed up query instead of relying on lazy individual gets
if isinstance(iterable, RelationshipResultList):
iterable = iterable.resolve()
edges = [
edge_type(node=entity, cursor=to_cursor(entity))
for entity in iterable
]
return [has_next, edges]
def hash_key_name(self):
if not self._hash_key_name:
self._hash_key_name = get_key_name(self.model)
return self._hash_key_name