Can't seem to filter for dash "-"?

Users Dgraph
1

What I want to do

Some predicates have a single dash as their field and I want to delete those, so I start by writing a query for it when I ran into the problem that I can’t filter for it

What I did

Schema for the predicate:

<User.altID>: string @index(fulltext, trigram) .

Query

query{
    User (func: type(User), first:100) @filter(eq(User.altID, "-")) {
        uid
        User.altID
    }
}

Results

{
  "data": {
    "User": []
  },

Just for reference here’s a query without the filter

	User (func: type(User), first:100) {
    uid
		 User.altID
	}
}

Results

{
  "data": {
    "User": [
      {
        "uid": "0x3c734a5a",
        "User.altID": "QR-513476"
      },
      {
        "uid": "0x3d0e7663",
        "User.altID": "-"
      },
      {
        "uid": "0x3d0e7669",
        "User.altID": "-"
      },
      {
        "uid": "0x3d0e766d",
        "User.altID": "QE-902215"
      },
      {
        "uid": "0x3d0e766f",
        "User.altID": "-"
      },
      {
        "uid": "0x3d0e7675",
        "User.altID": "-"
      },
...
2

This is a duplicated of

and