Find $nearSphere result with zero distance from queried point - mongodb

Question

I have the following record in my mongoDb:
{
"_id" : ObjectId("56e63313059484f212a4305f"),
"title" : "The video title",
"location" : {
"coordinates" : [
-73.9667,
40.78
],
"type" : "Point"
},
}
I want to be able to find all the points at that exact location.
If I write:
db.videos.find({
location: {
'$nearSphere': {
'$geometry': {
type: 'Point',
coordinates: [-73.9667, 40.78]
},
'$maxDistance': 0
}
}
})[0]
I don't get any results. If I type:
db.videos.find({
location: {
'$nearSphere': {
'$geometry': {
type: 'Point',
coordinates: [-73.9667, 40.78]
},
'$maxDistance': 0.00001
}
}
})[0]
I get the one result.
I looked and looked, and nowhere in the docs say that maxDistance cannot be 0.
Can it?

Answer 1

So as would make sense, $maxDistance set to 0 would be ignored just as if you had not set the option.
If you are looking for an "exact match" then just ask for that. It's not a $nearSphere query by any description:
db.videos.find({
"location.coordinates" : [ -73.9667, 40.78 ]
})
Which will of course return the document matching that "exact" location.
For something a little more complex, then use aggregation $geoNear instead. It projects a "distance" which you can use in later filtering:
db.videos.aggregate([
{ "$geoNear": {
"near": {
"type": "Point",
"coordinates": [ -73.9667, 40.78 ]
},
"distanceField": "distance",
"spherical": true
}},
{ "$match": { "distance": 0 } }
])
So the intial pipeline stage returns a "distance" and the second stage filters out any results where that distance was in fact 0.
You really only should need that if your queried objects were something like a "Polygon" or other GeoJSON form that would not match the "exact" coordinates array.
The general "exact" array match should suit for "Point" data.