Confused about geoWithin query.

[jfgo...@hivemapper.com]

Anyone know why these geoWithin queries don't behave as expected? I think I'm just missing something simple. I tried this on Mongo versions 2.6 and 3.

> use test

switched to db test

> db.dropDatabase()

{ "dropped" : "test", "ok" : 1 }

> db.test.createIndex({grid:'2dsphere'})

{

"createdCollectionAutomatically" : true,

"numIndexesBefore" : 1,

"numIndexesAfter" : 2,

"ok" : 1

}

// make a square, coordinates start at NW corner

> db.test.insert({grid:{type:'Polygon',coordinates:[[[1,2],[2,2],[2,1],[1,1],[1,2]]]}})

WriteResult({ "nInserted" : 1 })

// find the square inside the square

> db.test.find({grid: { $geoWithin: { $geometry: { type: "Polygon", coordinates: [[[1,2],[2,2],[2,1],[1,1],[1,2]]] } } } })

{ "_id" : ObjectId("5531aa43fb4a314ff06590d9"), "grid" : { "type" : "Polygon", "coordinates" : [ [ [ 1, 2 ], [ 2, 2 ], [ 2, 1 ], [ 1, 1 ], [ 1, 2 ] ] ] } }

// square is missing from various rectangles including the square but extending in different directions, $geoIntersects works

> db.test.find({grid: { $geoWithin: { $geometry: { type: "Polygon", coordinates: [[[0,2],[2,2],[2,1],[0,1],[0,2]]] } } } })

> db.test.find({grid: { $geoWithin: { $geometry: { type: "Polygon", coordinates: [[[0,2],[3,2],[3,1],[0,1],[0,2]]] } } } })

> db.test.find({grid: { $geoWithin: { $geometry: { type: "Polygon", coordinates: [[[0,3],[3,3],[3,1],[0,1],[0,3]]] } } } })

// square is present in larger square

> db.test.find({grid: { $geoWithin: { $geometry: { type: "Polygon", coordinates: [[[0,3],[3,3],[3,0],[0,0],[0,3]]] } } } })

{ "_id" : ObjectId("5531aa43fb4a314ff06590d9"), "grid" : { "type" : "Polygon", "coordinates" : [ [ [ 1, 2 ], [ 2, 2 ], [ 2, 1 ], [ 1, 1 ], [ 1, 2 ] ] ] } }

Appreciate any help!

- John

[Asya Kamsky]

Hi John,

The geoWithin doc page says that an object has to be *entirely* contained to satisfy the query.

http://docs.mongodb.org/manual/reference/operator/query/geoWithin/

Are you thinking of it in reverse (contains vs contained in)?

Asya

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[jfgo...@hivemapper.com]

Hi Asya, yes, I do understand that the document must be entirely within the shape in the query. Isn't that the case here?

I.e. isn't this square in the doc

{type:'Polygon',coordinates:[[[1,2],[2,2],[2,1],[1,1],[1,2]]]}

entirely contained in this rectangle in the query

{ type: "Polygon", coordinates: [[[0,2],[2,2],[2,1],[0,1],[0,2]]] }

so that the query should return the doc? But as the console output below shows, the query does not return it.

[Asya Kamsky]

Looks like they share some coordinates.  I don't believe that containment allows for intersection...

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