Usage of a variable in a conditional Upsert operation

Users Dgraph
1

For example I have a upsert operation like this,

upsert{
        query{
             k as var(func: eq(predicate, <string>)){
                 A as price
             }
            var(){
              changed_value as math(a - 50)
            }
       }     
       mutation @if(gt(changed_value, 0)){
           set{
                     uid(k) <predicate> changed_value .
               }
        }
}

When try to use the created variable from the query part for assigning a value to a predicate in the mutation part I get an error

{
  "name": "t",
  "url": "http://localhost:8080/mutate?commitNow=true",
  "errors": [
    {
      "message": "while lexing uid(k) <predicate> changed_quantity . at line 1 column 25: Invalid input: c at lexText",
      "extensions": {
        "code": "ErrorInvalidRequest"
      }
    }
  ]
}

Should one not use a variable for assigning values to a predicate ?

2

Dgraph variables are case sensitive.

This probably should be like

@if(gt(val(changed_value), 0))