QueryWithVars on facet filtering fails silently

[shanghai-Jerry]

If you suspect this could be a bug, follow the template.

• What version of Dgraph are you using?
  v1.0.6

• Have you tried reproducing the issue with latest release?
  No

• What is the hardware spec (RAM, OS)?
  Ubuntu, 128G

• Steps to reproduce the issue (command/config used to run Dgraph).
  nohup dgraph zero -w zw5 --replicas 1 > info1 &
  nohup dgraph server -p p5 -w w5 --lru_mb 20000 --zero localhost:5080 > info2 &
  nohup dgraph-ratel > info3 &

• Expected behaviour and actual result.

  i found a problem with query like this:

query withvar($a:string, $b:bool) {

query(func:uid($a)) {

candidate_school @facets(eq(on_edu,$b)) @groupby(name) {

  count(uid)
}
}
}

it doesn't have any result return, but when i use query like this:

{
query(func:uid(0x998a17)) {

candidate_school @facets(eq(on_edu,false)) @groupby(name) {

  count(uid)

}
}
}

it has result.

it seems that queryWithVars has a problem when query vars in facets.
@pawanrawal @sboorlagadda

refer ： https://discuss.dgraph.io/t/query-and-querywithvars/2796/9

[campoy]

This request makes total sense and should be considered at the same time as the others in the label https://github.com/dgraph-io/dgraph/labels/area%2Fquerylang%2Fvars

[campoy]

I reproduced this error.

Given this dataset:

{
  set {
    _:f <name> "Francesc" .
    _:f <works_in> _:sf (since="2018") .
    _:m <name> "Manish" .
    _:m <works_in> _:sf (since="2019") .
    _:i <name> "Ibrahim" .
    _:i <works_in> _:bg (since="2019") .
    _:sf <name> "San Francisco" .
    _:bg <name> "Bangalore" .
  }
}

I can query when someone started working and where with the following query:

query works($since: string = "2018") {
  q(func: has(works_in)) @cascade {
    name
    works_in @facets {
      name
    }
  }
}

This returns the following:

{
  "data": {
    "q": [
      {
        "name": "Manish",
        "works_in": [
          {
            "name": "San Francisco",
            "works_in|since": "2019"
          }
        ]
      },
      {
        "name": "Ibrahim",
        "works_in": [
          {
            "name": "Bangalore",
            "works_in|since": "2019"
          }
        ]
      },
      {
        "name": "Francesc",
        "works_in": [
          {
            "name": "San Francisco",
            "works_in|since": "2018"
          }
        ]
      }
    ]
  }
}

Now, we can filter by those that started working after 2018:

query works($since: string = "2018") {
  q(func: has(works_in)) @cascade {
    name
    works_in @facets @facets(gt(since, $since)) {
      name
    }
  }
}

This result is wrong, as you can see by the fact that 2018 results like "Francesc" still appear

{
  "data": {
    "q": [
      {
        "name": "Manish",
        "works_in": [
          {
            "name": "San Francisco",
            "works_in|since": "2019"
          }
        ]
      },
      {
        "name": "Ibrahim",
        "works_in": [
          {
            "name": "Bangalore",
            "works_in|since": "2019"
          }
        ]
      },
      {
        "name": "Francesc",
        "works_in": [
          {
            "name": "San Francisco",
            "works_in|since": "2018"
          }
        ]
      }
    ]
  }
}

But if you replace the variable $since with the value "2018" the behavior is correct!

query works($since: string = "2018") {
  q(func: has(works_in)) @cascade {
    name
    works_in @facets @facets(gt(since, "2018")) {
      name
    }
  }
}

{
  "data": {
    "q": [
      {
        "name": "Manish",
        "works_in": [
          {
            "name": "San Francisco",
            "works_in|since": "2019"
          }
        ]
      },
      {
        "name": "Ibrahim",
        "works_in": [
          {
            "name": "Bangalore",
            "works_in|since": "2019"
          }
        ]
      }
    ]
  }
}