predicate is not deleted from "_predicates_"

[makitka2007]

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

• What version of Dgraph are you using?
  1.0.6

• Have you tried reproducing the issue with latest release?
  yes

• Steps to reproduce the issue (command/config used to run Dgraph).

when I remove predicate - it doesn't disappear from _predicate_ field whereas actually it doesn't exist anymore.

POST localhost:8081/alter

entity_key: string @index(hash) .

POST localhost:8080/mutate

{
    set {
        _:entity1 <entity_key> "entity1" .
        _:entity2 <entity_key> "entity2" .
        _:entity1 <has> _:entity2 .
	}
}

{
    "data": {
        "code": "Success",
        "message": "Done",
        "uids": {
            "entity1": "0x7a",
            "entity2": "0x7b"
        }
    },
    "extensions": {
        "server_latency": {
            "parsing_ns": 9890,
            "processing_ns": 7999410
        },
        "txn": {
            "start_ts": 337,
            "commit_ts": 338,
            "lin_read": {
                "ids": {
                    "1": 329
                }
            }
        }
    }
}

POST localhost:8080/query

{
	result(func: eq(entity_key, "entity1")) {
		_predicate_
		has {
			uid
		}
	}
}

{
    "data": {
        "result": [
            {
                "_predicate_": [
                    "has",
                    "entity_key"
                ],
                "has": [
                    {
                        "uid": "0x7b"
                    }
                ]
            }
        ]
    },
    "extensions": {
        "server_latency": {
            "parsing_ns": 12686,
            "processing_ns": 119183,
            "encoding_ns": 397711
        },
        "txn": {
            "start_ts": 343,
            "lin_read": {
                "ids": {
                    "1": 330
                }
            }
        }
    }
}

POST localhost:8080/mutate

{
    delete {
        <0x7a> <has> <0x7b> .
	}
}

{
    "data": {
        "code": "Success",
        "message": "Done",
        "uids": {}
    },
    "extensions": {
        "server_latency": {
            "parsing_ns": 7024,
            "processing_ns": 4936211
        },
        "txn": {
            "start_ts": 344,
            "commit_ts": 345,
            "lin_read": {
                "ids": {
                    "1": 331
                }
            }
        }
    }
}

POST localhost:8080/query

{
	result(func: eq(entity_key, "entity1")) {
		_predicate_
		has {
			uid
		}
	}
}

{
    "data": {
        "result": [
            {
                "_predicate_": [
                    "has",
                    "entity_key"
                ]
            }
        ]
    },
    "extensions": {
        "server_latency": {
            "parsing_ns": 24228,
            "processing_ns": 142555,
            "encoding_ns": 408005
        },
        "txn": {
            "start_ts": 346,
            "lin_read": {
                "ids": {
                    "1": 332
                }
            }
        }
    }
}

• Expected behaviour and actual result.
  "has" predicate should be removed from _predicate_

[makitka2007]

tested on 1.0.6 - the same behaviour, so updated issue with that

[MichelDiz]

I'm able to reproduce this, it seems to me related to #2212

If I do (this is after delete):

{

 result(func: eq(entity_key, "entity1")) {
   uid
   _predicate_
   entity_key
   has {expand(_all_)}
	}

 result2(func: has(has)) {
   uid
   _predicate_
   entity_key
   has {expand(_all_)}
      }
}

Returns:

{
  "data": {
    "result": [
      {
        "_predicate_": [
          "has",
          "entity_key"
        ],
        "uid": "0x5",
        "entity_key": "entity1"
      }
    ],
    "result2": [
      {
        "_predicate_": [
          "has",
          "entity_key"
        ],
        "uid": "0x5",
        "entity_key": "entity1"
      }
    ]
  }

before delete:

{
  "data": {
    "result": [
      {
        "_predicate_": [
          "has",
          "entity_key"
        ],
        "uid": "0x5",
        "entity_key": "entity1",
        "has": [
          {
            "entity_key": "entity2"
          }
        ]
      }
    ],
    "result2": [
      {
        "_predicate_": [
          "has",
          "entity_key"
        ],
        "uid": "0x5",
        "entity_key": "entity1",
        "has": [
          {
            "entity_key": "entity2"
          }
        ]
      }
    ]
  }

[MichelDiz]

This is partially fixed. By #2585 . In theory this fix would not have side effects with the existence of "ghost" predicates in the Node. But it still need to clean them.

A solution usage.

{
	result(func: has(has)) @filter(eq(entity_key, "entity1")) {
          entity_key
          uid
          has {
              uid
              }
          }
}

or

{
	result(func: eq(entity_key, "entity1") ) @filter(has(has)) {
          entity_key
          uid
          has {
              uid
              }
          }
}

[srfrog]

The original issue with _predicate_ is cache related, which should be resolved soon. @MichelDiz your test will return an error in 1.0.11. I'm going to close this, but re-open if you reproduce sans _predicate_.

[MichelDiz]

erro: : Unhandled pb.node expand with parent has
Not sure what is this, but if I change to other predicate, works.