# Weird behavior of reverse edge on one-to-one relation

**URL:** <https://discuss.dgraph.io/t/weird-behavior-of-reverse-edge-on-one-to-one-relation/4018>\
**Category:** Dgraph\
**Tags:** kind:bug\
**Created:** [February 11, 2019, 9:10am UTC](https://discuss.dgraph.io/t/weird-behavior-of-reverse-edge-on-one-to-one-relation/4018 "2019-02-11T09:10:11Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![charlie-wasp](https://yyz1.discourse-cdn.com/flex007/user_avatar/discuss.dgraph.io/charlie-wasp/32/1489_2.png) [@charlie-wasp](https://discuss.dgraph.io/u/charlie-wasp)\
**Post date:** [February 11, 2019, 9:10am UTC](https://discuss.dgraph.io/t/weird-behavior-of-reverse-edge-on-one-to-one-relation/4018/1 "2019-02-11T09:10:11Z")

</div>

Hi, everyone!

A month ago DGraph got an ability to set up 1-to-1 relations between nodes on a schema level (here’s the [PR](https://github.com/dgraph-io/dgraph/pull/2895)). That’s a great feature, and I wanted to incorporate it in my schema too.

However, I faced a strange behavior, when I query the reverse edge of such 1-to-1 relation. Here’s the schema I use:

```auto
<amount>: int .
<name>: string @index(exact) .
<op.destination>: uid @reverse .
<op.source>: uid @reverse .

```

And here’s the data:

```auto
{
  set {
      _:u1 <name> "Alice" .
      _:u2 <name> "Bob" .
      _:u3 <name> "Charlie" .
  
      _:op1 <amount> "1000" .
      _:op1 <op.source> _:u1 .
      _:op1 <op.destination> _:u2 .
  
      _:op2 <amount> "250" .
      _:op2 <op.source> _:u1 .
      _:op2 <op.destination> _:u3 .
    
      _:op3 <amount> "430" .
      _:op3 <op.source> _:u2 .
      _:op3 <op.destination> _:u1 .
  }
}

```

I want to get all operations, issued by Alice (that should be two operations). I send this query:

```auto
{
  alice_operations(func: eq(name, "Alice")) {
    ~op.source {
      amount
      op.destination { name }
    }
  }
}

```

That query returns me the next piece of data:

```auto
{
  "alice_operations": [
    {
      "uid": "0xde2c5",
      "~op.source": {
        "op.destination": {
          "name": "Bob"
        },
        "amount": 1000
      }
    }
  ]
}

```

So I’ve got a single object instead of an expected array. Also, it seems that the result varies between different data loading.

The more weird result I get, if I query only one predicate on `~op.source`:

Query

```auto
{
  alice_operations(func: eq(name, "Alice")) {
    uid
    ~op.source {
      amount
    }
  }
}

```

Response

```auto
{
  "alice_operations": [
     {
       "uid": "0xde2c5",
       "~op.source": {
         "amount": [
           250,
           1000
         ]
       }
     }
  ]
}

```

I still got only one object in response, but now for some reason, `amount` predicate is an array. For me, it was entirely unexpected.

Is it a bug or I don’t understand something?

I realize that this particular feature isn’t released yet, I ran all of the examples above on the master branch of DGraph (I used `go get ...` command to install it)

I tried to find any tests on such cases in the codebase, but no luck. However, I am a total newbie to DGraph code so I might overlook it easily

---

<div class="post-metadata">

**Author:** ![MichelDiz](https://yyz1.discourse-cdn.com/flex007/user_avatar/discuss.dgraph.io/micheldiz/32/11873_2.png) [@MichelDiz](https://discuss.dgraph.io/u/MichelDiz)\
**Post date:** [February 11, 2019, 2:36pm UTC](https://discuss.dgraph.io/t/weird-behavior-of-reverse-edge-on-one-to-one-relation/4018/2 "2019-02-11T14:36:42Z")

</div>

Those features are not ready yet. I do not recommend using them.  
Use only the binaries provided via Release page and Docker Hub.

Anyway, I’m going to look into the case. For it seems quite strange indeed.

---

<div class="post-metadata">

**Author:** ![martinmr](https://yyz1.discourse-cdn.com/flex007/user_avatar/discuss.dgraph.io/martinmr/32/1408_2.png) [@martinmr](https://discuss.dgraph.io/u/martinmr)\
**Post date:** [February 12, 2019, 12:31am UTC](https://discuss.dgraph.io/t/weird-behavior-of-reverse-edge-on-one-to-one-relation/4018/3 "2019-02-12T00:31:07Z")

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Thanks for your report. I took a look and this turned indeed to be a bug. In query.go we were treating the reverse of a non-list predicate as a non-list predicate when it should be treated as a list as your example shows. That’s why only one of the results were being shown. The bug fix also fixed the second query that was provided.

PR with the fix: [Fix bug retrieving reverse edges of non-list uid predicates. by martinmr · Pull Request #3005 · dgraph-io/dgraph · GitHub](https://github.com/dgraph-io/dgraph/pull/3005)

---

<div class="post-metadata">

**Author:** ![charlie-wasp](https://yyz1.discourse-cdn.com/flex007/user_avatar/discuss.dgraph.io/charlie-wasp/32/1489_2.png) [@charlie-wasp](https://discuss.dgraph.io/u/charlie-wasp)\
**Post date:** [February 18, 2019, 12:31pm UTC](https://discuss.dgraph.io/t/weird-behavior-of-reverse-edge-on-one-to-one-relation/4018/4 "2019-02-18T12:31:21Z")

</div>

I can see that PR above was merged, and I just tested examples I wrote here — all seem to work properly! Thank you for such quick fix!