Angular Input Autocomplete/PHP/MySQL

I'm looking to write a routine in Angular that will serve as a search/autocomplete function on an input.  

The examples that I see, however, on the tutorial sites are problematic though...IMHO.  They all put into the name scope the entire list.  The examples I see are all along the lines of:

var app = angular.module('myApp', ['ui.bootstrap']);
 
app.controller('autocompleteController', function($scope, $http) {
 getCountries(); // Load all countries with capitals
 function getCountries(){
 $http.get("ajax/getCountries.php").success(function(data){
 $scope.countries = data;
 });
 };
});

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which might be all well and good for something like a country list - where there are only X number of possible options.  Might as well just download the whole list and then sift through them.

But - what if there are thousands of possible options?  What I'd like is a query where every time the input changes (I assume on an onChange event) - the ajax query is fired again...so in the above example it would be like...

function getCountry(country) {
var app = angular.module('myApp', ['ui.bootstrap']);
 
app.controller('autocompleteController', function($scope, $http) {
 getCountries(); // Load all countries with capitals
 function getCountries(){
 $http.get("ajax/getCountries.php?country="+country).success(function(data){
 $scope.countries = data;
 });
 };
});
}

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Is that about the syntax I'd use?  I'm pretty new to Angular and have had dicey results trying to change scopes on the fly like that.