Neo4J with exists() returning an object and not a Boolean?-CodePudding

I am new to Neo4J and trying to check if a User node FOLLOWS another user node in my graph database and return a boolean if the relationship exists between the two nodes.

In my current query, I match the two users and then use exists() to see if the FOLLOW relationship exists between them but I got the error:

PatternExpressions are not allowed to introduce new variables: 'f'.

So I modified the query to below to introduce the f:FOLLOWS relationship to check if it exists for RETURN but instead of returning a boolean it returned an object and NOT a boolean. When I logged the return result to the console it says [object Object] and the keys are [ 'records', 'summary' ]

      MATCH (u1:User{userId: $reqUserId}), (u2:User {userId: $userId})
      MATCH (u1)-[f:FOLLOWS]->(u2)
      RETURN exists((u1)-[c]->(u2))

What am I doing wrong?

const checkIfUserCollectsUser = async (reqUserId, userId) => {
  let driver = neo4j.driver(
    process.env.NEO4J_URL,
    neo4j.auth.basic(process.env.NEO4J_USERNAME, process.env.NEO4J_PASSWORD)
  )

  let session = driver.session()

  return new Promise(async (resolve, reject) => {
    try {
      const readQuery = `
      MATCH (u1:User{userId: $reqUserId}), (u2:User {userId: $userId})
      RETURN exists((u1)-[f:FOLLOWS]->(u2))
    `
      const bool = await session.executeRead((tx) =>
        tx.run(readQuery, { reqUserId: reqUserId, userId: userId })
      )
     
      resolve(bool)
    } catch (err) {
      console.log(err.message)
      reject({ message: err.messages })
    } finally {
      await session.close()
    }

    await driver.close()
  })
}

CodePudding user response：

Your pattern (u1)-[f:FOLLOWS]->(u2) does not need a new variable f. It is not usable elsewhere. You simply remove it and it should work.

For example:

  MATCH (u1:User{userId: $reqUserId}), (u2:User {userId: $userId})
  RETURN exists((u1)-[:FOLLOWS]->(u2))

Result:

╒═════════════════════════════╕
│"exists((u1)-[:LINKS]->(u2))"│
╞═════════════════════════════╡
│true                         │
└─────────────────────────────┘