MongoDB can't parse query (2dsphere): $geoWithin: - mongodb

Question

I have the following objects in my Collection that look like the following:
{
"_id" : ObjectId("527d33a8623f6efd1c997440"),
"location" : {
"geometry" : {
"type" : "Point",
"coordinates" : [
-78.4067,
37.26725
]
},
"type" : "Feature",
"properties" : {
"name" : "Something here"
}
},
"name" : "Name of Object"
}
I have the following index:
{
"location.geometry" : "2dsphere"
}
I can do the following:
db.myCollection.find({'location.geometry':{'$near':{'$geometry':{'type':"Point", 'coordinates': [-78.406700,37.267250]}, '$maxDistance' : 1000 }}})
However, I can Not do the following:
db.myCollection.find( { 'location.geometry': { '$geoWithin':
{ '$geometry' :
{ 'type' : "Polygon",
'coordinates' : [ [ -118.108006, 34.046072], [ -117.978230, 34.041521] , [ -117.987328,33.913645 ]] } }
} } )
As it returns with the error:
error: {
"$err" : "can't parse query (2dsphere): { $geoWithin: { $geometry: { type: \"Polygon\", coordinates: [ [ -118.108006, 34.046072 ], [ -117.97823, 34.041521 ], [ -117.987328, 33.913645 ] ] } } }",
"code" : 16535
}
Am I using geoWithin wrong? Can it not be used on this index?

Answer 1

The polygon that you are providing for $geowithin query is incorrect. A polygon needs to have the same start and end point as per GeoJSON definition.
The correct query is:
db.myCollection.find( { 'location.geometry':
{ '$geoWithin':
{ '$geometry' :
{ 'type' : "Polygon",
'coordinates' : [
[ -118.108006, 34.046072],
[ -117.978230, 34.041521],
[ -117.987328,33.913645 ],
[ -118.108006, 34.046072]
]
}
}
}
}
);
Notice the updated coordinates array.
Clearly, what is mentioned here in MongoDB docs about implicit connection of Polygons is NOT incorrect. It says that when you define the polygon using $polygon in MongoDB, only then is the connection implicit. It says nothing about being smart and making an implicit connection in the GeoJSON polygon provided to the query.
In fact, if for some GeoJSON variable you are saying that its type is polygon and you are not connecting its start with the end, then you have not created a correct GeoJSON polygon in the first place.

Answer 2

There is an error in the MongoDB documentation on $geoWithin queries. While the documentation states that:
The last point specified is always implicitly connected to the first.
You can specify as many points, and therefore sides, as you like.
This is incorrect. The polygon needs to be closed. There is an open ticket about this in MongoDB Jira:
https://jira.mongodb.org/browse/DOCS-2029
So your first and last points need to be equal - you cannot depend on MongoDB to implicitly draw the last line of the polygon.