String array out of order

Users Dgraph
,
1

Very new user of Dgraph here but so far, loving it!

I’ve encountered a really strange bug(?) it seems

In my schema I have: Product.facts [string]

  const createProduct = new Mutation();
  const x = {
    "dgraph.type": "Product",
    "Product.attributes": "{\"string\":\"42\",\"number\":42,\"nested\":{\"nested\":\"property\"},\"boolean\":false}",
    "Product.brand": {
      "uid": "0x24f"
    },
    "Product.facts": [
      "test fact #1",
      "test fact #2",
      "test fact #3"
    ],
    "Product.media": [],
    "Product.name": "test product name",
    "Product.subtitle": "test product subtitle",
    "Product.description": "test product description",
    "uid": "_:product"
  }
  createProduct.setSetJson(x);
  createProduct.setCommitNow(true);

  const clientStub = new DgraphClientStub(<dgraph-url>, grpc.credentials.createInsecure());
const client = new DgraphClient(clientStub);
client.setDebugMode(true)
  const productId = await client.newTxn()
    .mutate(createProduct)
    .then(r => r.getUidsMap().get('product'))

Then I go to Ratel and check the inserted object, and I see:

{
  node(func: uid(<product ID>)) {
    Product.facts
  }
}

And I see:

        "Product.facts": [
          "test fact #2",
          "test fact #1",
          "test fact #3"
        ]

Why are strings out of order?

2

The list type in Dgraph behaves like an unordered set (i.e. does not guarantee order).

Primitive lists do not permit sorting. Instead, we can create separate nodes for each fact:

{
  set {
    _:f1 <description> "test fact #1" .
    _:f2 <description> "test fact #2" .
    _:f3 <description> "test fact #3" .
    _:p1 <has_fact> _:f1 .
    _:p1 <has_fact> _:f2 .
    _:p1 <has_fact> _:f3 .
  }
}

Now, we can easily sort the output:

{
  node(func: uid(0x6)) {
    has_fact(orderasc: description) {
      description
    }
  }
}
2 Likes
3

I see. Thanks!

6

FYI, I solved this for my use case by storing an ordered array as JSON in a string.

This may not fit your use case though. For my use case, 1) I will be updating the entire array at once and not item by item; 2) I will not need to search for the items in the array, although search indexing would work on the string such as anyofterms or alloftext depending on your applied indexing. 3) I will always need to entire list at once, I never need just a single item from the list.

1 Like