I am constructing an app (in XCode) which, in a general sense, displays information to users. The information is stored as individual objects in a database (happens to be a Parse-server hosted by heroku). The user can elect to "see" information that has been created within a set distance from their current location. (The information, when saved to the DB, is saved along with its lat and long based on the location of the user when they initiated the save). I know I can filter the pieces of information by comparing their lat and long to the viewing user's current lat and long and only display those which are close in enough. Roughly/generally:
var currentUserLat = latitude //latitude of user's current location var infoSet = [Objects] //set of all pulled info from DB for info in infoSet{ if info.lat-currentUserLat < 3{//arbitrary value //display the info }else{ //don't display } } This is set up decently enough, and it works fine. The reason it works fine, though, is because of the small number of entries in the DB at this current time (the app is in development). Under practical usage (ie many users) the DB may be full of information objects (lets say, a thousand). In my opinion, to individually pull and compare the latitude of the information and compare it to the current user's latitude for each and every DB entry would take too long. I know there must be a way to do it in a timely manner (think tinder... they only display profiles of people who are in the near vicinity and it doesn't take that long for them to do so despite millions of profiles) but I do not know what is most efficient. I thought of creating separate sections for different geographical regions in the DB and then only searching those particular section of the DB depending on where the user's current location is, but this seems unsophisticated and would still lead to large amounts of info being pulled. What is the best way to do this?
2 Answers
Answers 1
Is there a reason you need to do that sort of checking on the client side? I would suggest sending your coordinates to your server and then having the server query your database with those coordinates and figure out which items to pull based on the given coordinates respectively. Then you can have the server return back to the client side whichever items were "close" to that user
EDIT: reworded
Answers 2
Per Deploying a Parse Server to Heroku you can Install a MongoDB add-on or another of the Data Stores in the Add-on Category in which you can use Geospatial Indexes and Queries which are specifically intended for this sort of application.
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