Latcie:

I am trying to grab the uid given his Email.

I have this:

let usersRef = Database.database().reference().child("users")

    usersRef.queryOrdered(byChild: "email").queryStarting(atValue: email).queryEnding(atValue: email).observeSingleEvent(of: .value, with: { (snapshot) in
        if let values = snapshot.value as? [String: Any]{
            print(values)
        }
    })

And my database looks as follows:

users

| -$uid

| --email: "some email"

The Snapshot doesn't return anything.

Also, the debugger tells me this: Using an unspecified index. Your data will be downloaded and filtered on the client. Consider adding ".indexOn": "email" at /users to your security rules for better performance

I think I have done this like so:

{
  "rules": {
"users": {
  ".read": "auth != null",
  "$uid": {
    ".write": "$uid === auth.uid",
    ".indexOn": ["email"]
  }

But this doesn't work as well.