Pfthb

I have a MongoDB containing a large amount of coordinates, which I use to query for the nearest position to a provided one, e.g. if the DB contains coordinates (2,2) and (3,3) and gets queried for the nearest position to (1,1) it would return (2,2).

Using the java driver, I can perform the query the following way:

MongoConnection.getInstance().getCollection(DB, COLLECTION).find(new BasicDBObject(LOCATION, new BasicDBObject("$nearSphere", Arrays.asList(longitude, latitude)))).limit(1)

which works fine and returns the result quite fast (instantaneously). However, if the nearest position is very far way, this procedure still returns it and meanwhile I decided to retrieve such result only if it is within a radius R. Therefore I decided to employ $maxDistance:

BasicDBObject center = new BasicDBObject("$nearSphere", Arrays.asList(latitude, longitude));
center.put("$maxDistance", MAXDIST);
MongoConnection.getInstance().getCollection(DB, COLLECTION).find(new BasicDBObject(LOCATION, center)).limit(1)

Which returns the expected result, however it takes about 5 seconds to do so.

I realize that I can circumvent this issue simply by using the former method and perform a simple logical test on the value returned, however I would like to understand why the latter procedure is so much slower than the former. Am I doing anything wrong?

Thank you for your attention