How can I filter a type that holds a specific predicate uid?

Users Dgraph
1

How can I filter a type that holds a specific predicate uid?
Example schema:

type Product {
	id: ID!
    brand(filter: BrandFilter): Brand! @hasInverse(field: products)
}


type Brand {
    id: ID!
    name: String! @id @search
    products: ...
}

....

So can I get a Product that has a Brand with uid=“0x12345”?

Obviously filtering the brand like below doesn’t work because it returns all Products instead and one of them contains the brand with the 0x12345 uid as well. Instead, I need to get the whole Product that has that brand.

{
query(func: type(Product)){
  uid
  Product.brand @filter(uid("0x12345")){
    uid
    expand(_all_)
  }
}
}

Dgraph metadata

dgraph version

v21.12.0

2

If you have the UID you can just query for it. This is not SQL, you do not need to start with the table/type and filter it further. Instead just start with what you actually want.

{
    query(func: uid(0x1234)){
        uid
        expand(_all_)
    }
}

If you want to make sure that the uid is part of a type definition, you can filter for it:

{
    query(func: uid(0x1234))@filter(type(some_type)){
        uid
        expand(_all_)
    }
}
1 Like
3

@vnium Thanks for the response. Let me add more context. I don’t have the Product ID. I have only the Brand uid. I need to get the Product that holds the Brand with uid 0x1234. I tried everything that is in the Dgraph documentation. It seems that there is no way to do it with filters. I wonder if I need to do multiple queries here with upsert.

4

Try the query below. This will start with Brand node 0x12345 and expand to all associated products.

{
    query(func: uid("0x12345")){
        Brand.products{
            uid
            expand(_all_)
        }
    }
}
5

Thanks @vnium

Is there any way to get multiple uids for Brands based on another query and add them as filters?

6

Yes, check “Query Variables” and “Value Variables” in the DQL docs. You can try something like below:

{

    var(func: <some_query_to_get_brands>){
        variableWhichHoldsAllSelectedBrands as uid
    }
    
    q(func: uid(variableWhichHoldsAllSelectedBrands)){
        Brand.products{
            uid
            expand(_all_)
        }
    }
}

This would return all products of all selected brands.

1 Like
7

If you have a list of uids and you want to filter a list on entities having a relation (a predicate) to those uid, consider using uid_in function in a filter :
https://dgraph.io/docs/query-language/functions/#uid_in

function uid_in allows looking ahead along an edge to check that it leads to a particular UID.

2 Likes