Does Weaviate allow classes to have self-referential properties?

Support
1

Question that I am very surprised I cannot find an answer to –

Does Weaviate allow a class to have a property that is its own class (i.e. a self-reference). For example I can have a document that has a property that references another object of the document class. This is of course a common feature in other document databases. Is it possible with Weaviate? If yes, are there any concerns I should have with implementing it? e.g.

{
  "class": "Document",
  "properties": [
    {
      "name": "title",
      "dataType": ["string"]
    },
    {
      "name": "parentDocument",
      "dataType": ["Document"]
    }
  ]
}

Thank you!

2

Hi @gsVAM !! Welcome to our community!!

That’s a really good question, which I don’t have the answer. Yet. :sweat_smile:

I’ll ping our core team about it.

Thanks for asking!

3

Hi @gsVAM! Here it is:

class_obj = {
  "class": "Document",
  "properties": [
    {
      "name": "title",
      "dataType": ["string"]
    },
    {
      "name": "parentDocument",
      "dataType": ["Document"]
    }
  ]
}
# lets create our class
client.schema.create_class(class_obj)
# lets predefine our uuids
d1_uuid = weaviate.util.generate_uuid5("document1")
d2_uuid = weaviate.util.generate_uuid5("document2")
print("document1", d1_uuid)
print("document2", d2_uuid)
# create objects
document1 = client.data_object.create({"title":"Document 1"}, "Document", d1_uuid)
document2 = client.data_object.create({"title":"Document 2"}, "Document", d2_uuid)
# add references
client.data_object.reference.add(
        from_class_name="Document",
        from_uuid=d1_uuid,
        from_property_name="parentDocument",
        to_class_name="Document",
        to_uuid=d2_uuid        
    )

now to query this self referential property:

client.query.get("Document", ["title", "parentDocument{...on Document{title}}"]).do()

the resulting Graphql:

{
  Get {
    Document {
      title
      parentDocument {
        ... on Document {
          title
        }
      }
      _additional {
        id
      }
    }
  }
}

and finally the json response:

{'data': {'Get': {'Document': [{'_additional': {'id': '41fdaad0-e1b2-5d0e-a486-b9b519029264'},
     'parentDocument': None,
     'title': 'Document 2'},
    {'_additional': {'id': 'd895dd7c-deb6-5d5f-8129-379990b2f866'},
     'parentDocument': [{'title': 'Document 2'}],
     'title': 'Document 1'}]}}}

This is the documentation where it states how to add those references :slight_smile: