In Neo4j, how can we store the key value pairs obtained after generating a query into another existing node using graphql?

Question

I am using Neo4j 3.2 and graphql in nodejs. I have 2 types "School" and "Class" with following relationship:

(School)-[:has]->(Class)// 1 school can have multiple classes .

Their data structure along with relationship in neo4j is similar to the one below:

School{ id: 001, label: "School A"}-[:has]->Class{ id: 001, label: "Class 1"}
School{ id: 001, label: "School A"}-[:has]->Class{ id: 002, label: "Class 2"}

What I am trying to do is to pull the count of classes present in a particular school and store/append this count value (as property) in already existing 3rd type "SchoolData" which has following relation with "School" type. (SchoolData)-[:of]->(School). So as from above example, the count of classes i.e. 2 needs to be stored in "SchoolData" for School A. i.e.

(SchoolData{ classCount: 2, label: "School A", otherInfo: "Already exisiting values are present here" })-[:of]->(School { id: 001, label: "School A"})

I have made a mutation to do so, but the data returned after generating count through cypher is not being stored in the node "SchoolData". Can some one please let me know why i am getting null and how should I handle it?

Here is my graphql type along with the mutation query:

type SchoolData{
   classCount: Int
   label: String
   otherInfo: String
}
// mutation query
countThenAddIntoSchoolData( schoolID: String! ): SchoolData

Here is my resolver mutation query of graphql:

 countThenAddIntoSchoolData(_, params) {
  let classCount = `MATCH (s:School {id: $schoolID })-[:has]->(c:Class) return count(c) as c`;
  let label = `MATCH (s:School {id: $schoolID })-[:has]->(c:Class) return s.label as s`;


  let sessionData = {};
  return Promise.all([
      getDBSession(sessionData).run(classCount, params),
      getDBSession(sessionData).run(label, params)
    ]).then((result) => {
      let data = {
        classCount: result[0].records.map(record => {
          return record.get('c');
        }),
        label: result[1].records.map(record => {
          return record.get('s');
        })
      };
      return data; // till here, it works fine
    }).then((data) => {
      let saveQuery = `MATCH (sd:SchoolData)-[:of]->(s:School {id: $schoolID })
                        SET sd += $data `
      return getDBSession(sessionData).run(saveQuery, params);

    })
    .catch((e) => {

    });
}

Note: getDBSession is already configured in my another file (database.js).

Here is my object "data" returned from Promise.all:

    data:{ 
   classCount: [ Integer { low: 2, high: 0 } ],
   label: [ 'School A' ]
  }

// The solved final query (thenable part):

    .then((data) => {

       params['data'] = {
         classCount: data.classCount[0],
         label: data.label[0]
       };
          let saveQuery = `MATCH (sd:SchoolData)-[:of]->(s:School {id: 
                           $schoolID })
                            SET sd += $data `
          return getDBSession(sessionData).run(saveQuery, params);

        })
        .catch((e) => {

        });
    }

And here is the output of the "SchoolData":

  {
   "classCount": 2,
   "label": "School A"
   "otherInfo": "Details of relevant school..."
  }

When the Promise returned by getDBSession(sessionData).run(saveQuery, params) resolves, what does the resulting object look like? — Daniel Rearden
it ireturns null, and no any properties are being appended for schoolData node. BTW, Thanks a lot for your effort. Really appreciable ! — Code Reactor

William Lyon William Lyon · Accepted Answer · 2018-03-01T23:28:14

I think you might need to convert the Integer object returned from the first query into a JavaScript Number before passing it as a parameter in the second query:

return record.get('c').toInt()

The JavaScript Neo4j driver uses a custom Integer object to represent integers, since there is no Int type in JavaScript.

Can you add a console.log(e) in your catch so you can see any errors that occur?

In Neo4j, how can we store the key value pairs obtained after generating a query into another existing node using graphql?

1 Answers