Update one-to-many relationship

Users Dgraph
1

Hi,
I have the schema

uuid: string @index(hash) .
owner: uid @reverse .

type Owner {
    uuid: string
    <~owner>
}

type Device {
    uuid: string
    owner: Owner
}

The owner has many devices, the device has one owner

And the next data

_:foo <uuid> "foo" .
_:foo <dgraph.type> "Owner" .

_:bar <uuid> "bar" .
_:bar <dgraph.type> "Owner" .

_:baz <uuid> "baz" .
_:baz <dgraph.type> "Device" .
_:baz <owner> _:foo .

I want to change the device owner - from foo to bar, so I run the upsert

query {
  device as var(func: eq(uuid, "baz")
  owner as var(func: eq(uuid, "bar")
}

mutation {
  set {
    uid(device) <owner> uid(owner) .
  }
}

The question is if it is right to make upsert in this way? Because after this upsert relation between baz-device and foo-owner still exists
Or should I delete old relation and only then add a new one?

2

Hi @poketulhu,

The mutation that you are doing is adding a new relation independent of the older relations. If you want to remove some relation then you should delete it as well.

3

Then I have another problem: if I delete and set in the same mutation and old and new owners are the same, then delete overwrites set. So I lose relation between device and owner.
What to do in this case?

4

I think it is related to this bug, that ~reverse doesn’t update correctly: Reverse index doesn't update for non-list uid predicates · Issue #5732 · dgraph-io/dgraph · GitHub

5

Hey @poketulhu, your mutation looks good to me. Ideally, your mutation should set the <owner> to the new owner and delete the reverse edge for the previous owner to the device. There is a bug that @reverse edge is not being updated correctly which @ppp225 has pointed out.

7

So there’s no need to delete before the update? Is the estimated deadline for fixing this bug known?

8

Yes,there is no need to delete in your case.

Our team will try to pick up this ASAP.

9

Many thanks for the help!