How to update information in an existing node instead of creating a new one using Dgraph using golang?

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1

I am writing a Golang application using Dgraph for persisting objects. From the documentation, I can infer that a new UID and hence a new node is created everytime I mutate an object/run the code.

Is there a way to update the same node data instead for creating a new node?

2

Hi,
I assume you are inserting blank nodes, and are putting on some unique ID controlled on your end?

If so, read up on upserts using externally controlled IDs.

3

@iluminae I am using uid which is generated by dgraph itself. When I run the code, there is no error but the record in my dgraph does not get any updated.
Here is my code, hope you can help.

func (dg *Dgraph) UpdateOrderState(ctx context.Context, jwt string, id string, state string, chargeId string) ([]byte, error) {
	o := &models.Order{Uid: id, State: state, StripeChargeId: chargeId}
	md := metadata.New(map[string]string{"Content-Type": "application/grpc", "Authorization": jwt, "auth-token": jwt})
	ctx = metadata.NewOutgoingContext(ctx, md)

	ojson, err := json.Marshal(o)
	if err != nil {
		log.Printf("Could not marshal order - %s", err)
		return []byte{}, err // invalid order
	}

	mu := &api.Mutation{
		SetJson:   ojson,
		CommitNow: true,
	}

	txn := dg.client.NewTxn()

	res, err := txn.Mutate(ctx, mu)
	if err != nil {
		log.Printf("error updating order - %s", err)
		return []byte{}, err // skip if broken at this stage
	}

	// defer txn.Discard(ctx)
	log.Printf("ORDER UPDATED: %s", res.GetJson())
	return res.GetJson(), nil
}
4

Ah the json mutation format - I assume something is wrong with the rendered json after the marshal. Read here about using existing uids in the json mutation format.

Also I would highly suggest using the protobuf nquad api (Set on the Mutation) to know exactly what you are doing in a type-safe way, but good luck either way.

5

Sorry still have no luck for both of them :sob:

6

can you share a literal input to Mutate that is not working rather than the code? Work backwards from just sending the literal string {"uid":"0x1","field":"value1"} and testing with that?