Checking for child causes poor scalability?

问题

This isn't a question that nessacarily has a 'solution', but I was wondering if this code would cause memory issues when scaled much larger.

        ref.child("Teams").observeSingleEvent(of: .value, with: { (snapshot) in
            if snapshot.hasChild(self.teamName.text!){
                //Sets the a single team's values
            } else {
                //Displays a missing team alert
                let alert = UIAlertController(title: "Error" , message: "Team does not exist", preferredStyle: .alert)
                let actio1n = UIAlertAction(title: "Ok" , style: .cancel , handler: nil)
                alert.addAction(actio1n)
                self.present(alert, animated: true, completion: nil)
            }
        })

I'm sort of wondering if Firebase would just load the surface level (each individual team's ID), or if it would load more in-depth. What are your thoughts?

回答1:

Firebase will fetch the FULL tree under Teams. More details here:

[...] when you fetch data at a location in your database, you also retrieve all of its child nodes [...]

回答2:

As Mihai said: observing a node will retrieve that entire node.

To check if a specific child node exists, observe only that child node:

ref.child("Teams").child(self.teamName.text!).observeSingleEvent(of: .value, with: { (snapshot) in
    if snapshot.exists(){
        ...
    }
})

来源：https://stackoverflow.com/questions/43213048/checking-for-child-causes-poor-scalability