使用纬度和经度按距离存储和分类Symfony2学说

Question

I am working in Symfony2 with Doctrine.

I have a database of entities named Landmarks where each entity has a 1:many relationship with a MapMarker entity, and it is the MapMarker entity which has a latitude and longitude field, eg "Central Park" might be a Landmark with many "entrances" which would be stored as MapMarkers .

I then have another entity named Property , which has a 1:1 relationship with a MapMarker .

For any given Property , What is the best way to find all the nearby Landmarks in the database, sorted by the Landmark's closest MapMarker ?

In a legacy version of this application, without Doctrine or Symfony2, I was doing it this way:

1. Retrieve all the Landmarks in database

2. For each Landmark , go through each of its MapMarkers in a PHP function and calculate the distance between the P roperty's MapMarker's lat,lng and the Landmarks MapMarker's lat,lng .

3. If any of the calculated distances was less than or equal to some pre-determined constant I had chosen (say 3km) then I made linked the Property to the Landmark in a many:many relatioship.

4. Later, when querying the database for a Property's nearby Landmarks , it would go through only the linked Landmarks ' MapMarkers and then calculate, again, the nearest MapMarker and distance for presentation like such:

Nearby Landmarks to your Property:

• Central Park , Main Gate - 2.4km
• etc.

The benefits of this were that it by creating a permanent link between the Property and the Landmark , I automatically had a "short-list" of nearby Landmarks for which to calculate the expensive distance formula.

However as you likely noticed, problems arise when a new Landmark is added, or the MapMarkers of a Landmark change. Also, it is still quite slow to be calculating the distance every time a Property is searched (or reverse if finding all Properties by Landmark ).

Really hoping to come up with a better way now that I am migrating to Symfony2 and Doctrine.

Any ideas?

Answer 1

Well Symfony2 and Doctrine won't free you from your usual database / PHP constraints so it is pretty much a matter of adapting your existing logic to it.

With that said and of the top of my head I would probably do something like:

• Join Query the database with a BETWEEN on latitude/longitude (ie: lat between marker_lat + X / marker_lat - X and long between marker_long + X / marker_long - X) to get a short list of close by mapmarkers
• Write a function to calculate distance and keep the closest

Rather than make a whole new table with number of markers * X entries which makes for poor scalability if you ask me but obviously it depends on your application constraints so I can't really think that through for you.