Custom DQL Query Result is Always Empty

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1

Hi,

I am trying to get a custom DQL query to work in a GraphQL setting, but my response is always empty.
I have tried to shrink it down to a minimal example and still no success.

This is my schema:

POST http://localhost:8080/admin/schema

type Person {
  id: ID!
  firstName: String!
  lastName: String!
}

type Query {
  queryPersonCustom : [Person] @custom(dql: """
    query {
      queryPersonCustom(func: uid(0x2)) {
        id : uid
        firstName : Person.firstName
        lastName : Person.lastName
      }
    }
  """)
}

I am adding a person like this:

POST http://localhost:8080/graphql
Content-Type: application/graphql

mutation {
  addPerson(input: [{ firstName: "Harry", lastName: "Potter" }]) {
    person {
      firstName
      lastName
    }
  }
}

and it is assigned the uid 0x2, as I can check with this query:

POST http://localhost:8080/graphql
Content-Type: application/graphql

query {
  queryPerson(filter: {id: "0x2"}) {
    id
    firstName
    lastName
  }
}

This returns { "id": "0x2", "firstName": "Harry", "lastName": "Potter" } as expected.
Also, my DQL is working in theory:

POST http://localhost:8080/query
Content-Type: application/dql

query {
  q(func: uid(0x2)) {
    id : uid
    firstName : Person.firstName
    lastName : Person.lastName
  }
}

This returns { "id": "0x2", "firstName": "Harry", "lastName": "Potter" } as well.

But calling the custom query via GraphQL always produces an empty result:

POST http://localhost:8080/graphql
Content-Type: application/graphql

query {
  queryPersonCustom {
    id
    firstName
    lastName
  }
}

Can anyone tell me why? What am I missing?
Also: Is there a way to see what’s going on as dgraph processes my query? Can I somehow find out whether the DQL query’s result is empty or whether something goes wrong while mapping to GraphQL?

Thanks in advance!
Stefan

2

I’ve just followed your steps and it is working as you expected.

image
image1264Ă—864 45 KB

3

Thanks for the quick reaction.
For me it isn’t :frowning:

screenshot-1
screenshot-11540Ă—994 65.3 KB

Your screenshot seems to show a regular GraphQL query. That’s working for me as well.
It is my queryPersonCustom DQL query (see schema) that’s not working.

What can I do to find out what is going wrong?

4

humm, I think you have to use has instead of func: uid(0x2)

5

Yep, I can confirm that using has(Person.firstName) works. The problem is the following.
func: uid(0x2) Returns a single object, and has(Person.firstName) returns an array. If you wanna just a single object you need to turn that query single instead of array.

1 Like
6

Cool, yes that works :slight_smile:

But why does func: uid(0x2,0x3) not work then? This also returns an array (I even added another person, so in my DB there is now also a person with UID 0x3 and still the query with func: uid(0x2,0x3) is empty.

What I actually want to achieve, is to pass a list of uids to the DQL, as in this post.

So this is my schema with DQL:

POST http://localhost:8080/admin/schema

type Person {
  id: ID!
  firstName: String!
  lastName: String!
}

type Query {
  queryPersonCustom(ids: String!) : [Person] @custom(dql: """
    query q($ids : string) {
      queryPersonCustom(func: uid($ids)) {
        id : uid
        firstName : Person.firstName
        lastName : Person.lastName
      }
    }
  """)
}

and this is my concrete request:

POST http://localhost:8080/graphql
Content-Type: application/graphql

query {
  queryPersonCustom(ids: "[0x2,0x3]") {
    id
    firstName
    lastName
  }
}

Again, the result is empty :frowning:

7

dunno, there are some dark magic in the GraphQL code that I’m not worthy to understand LOL
I didn’t work on that code, so I don’t know how it parses it.

Try this please

  query q($ids : string = "[0x2712, 0x1]") {
      queryPersonCustom(func: has(Person.firstName)) @filter(uid($ids)) {
        id : uid
        firstName : Person.firstName
        lastName : Person.lastName
        dgraph.type
      }
}

BTW, can you do something for me?
Can you try without square brackets?
It should return an error or the complete error like this

strconv.ParseUint: parsing \"0x2712,0x1\": invalid syntax

Also add the default value after this test

query q($ids : string = "[0x2712, 0x1]") {

This above is the sintax for default value in DQL.

1 Like
8

Ha! I got it working:

This is the schema / DQL:

POST http://localhost:8080/admin/schema

type Person {
  id: ID!
  firstName: String!
  lastName: String!
}

type Query {
  queryPersonCustom(ids: String!) : [Person] @custom(dql: """
    query q($ids : string) {
      queryPersonCustom(func: type(Person)) @filter(uid($ids)) {
        id : uid
        firstName : Person.firstName
        lastName : Person.lastName
      }
    }
  """)
}

and this is the query:

POST http://localhost:8080/graphql
Content-Type: application/graphql

query {
  queryPersonCustom(ids: "[0x2,0x3]") {
    id
    firstName
    lastName
  }
}

About your question:

If I use queryPersonCustom(ids: "0x2,0x3") { ... } I get the error message resolving queryPersonCustom failed because got error while rewriting DQL query because strconv.ParseUint: parsing “0x2,0x3”: invalid syntax.

And the same error message is also shown if I use "0x2,0x3" as default value in the DQL query in the schema and leave out the ids parameter in the query execution.

Thank you so much for your quick support @MichelDiz !

9

Cool, I would prefer to use eq(dgraph.type, "Person") or has(with a limited set of objects) due to performance. But that is just a choice for the future. It doesn’t make any difference now.

1 Like