Mongodb Sphere index rejects my object

Question

Hi i have an COllection with an 2d sphere index

wayCollection.createIndex(new BasicDBObject("poly", "2dsphere"));

i when i try to insert a certain object i get an error:

Exception in thread "main" com.mongodb.WriteConcernException: { "serverUsed" : "localhost:27017" , "ok" : 1 , "n" : 0 , "err" : "insertDocument :: caused by :: 16755 Can't extract geo keys from object, malformed geometry?: { _id: ObjectId('53a89dc6a0042baf54050037'), id: 24837452, version: \"64\", changeset: \"13731788\", uid: \"362915\", user: \"micha555\", timestamp: \"2012-11-03T09:11:23Z\", poly: { type: \"Polygon\", coordinates: [ [ [ 9.1244131, 50.0109503 ], [ 9.120464800000001, 50.0099731 ], [ 9.116641, 50.0077

although the multipolygon ring is closed (first and last coordinate is the same)

any ideas?

Here is another polygon which is rejected:

{
   "type":"Polygon",
   "coordinates":[
      [
         [
            9.0496053,
            51.3255584
         ],
         [
            9.0492235,
            51.32532
         ],
         [
            9.0495831,
            51.3251321
         ],
         [
            9.049917199999999,
            51.3253429
         ],
         [
            9.0496053,
            51.3255584
         ],
         [
            9.049984500000001,
            51.3258463
         ],
         [
            9.0505795,
            51.3262127
         ],
         [
            9.050045600000001,
            51.326574
         ],
         [
            9.0496432,
            51.3263928
         ],
         [
            9.049625300000001,
            51.3262806
         ],
         [
            9.0495628,
            51.3261244
         ],
         [
            9.0495316,
            51.3259341
         ],
         [
            9.0495471,
            51.3257127
         ],
         [
            9.0496053,
            51.3255584
         ]
      ]
   ]
}

when i paste it here it seems to be ok: http://geojsonlint.com/

maybe mongo db does not like when a point is used twice

Answer 1

First thing I would do is check your polygon at http://geojsonlint.com/ . If it does not pass then you know you have an issue with your data points (which has caused this error for many people previously).

If it does pass then I would check this bug that was recently reported and submitted to MongoDB: https://jira.mongodb.org/browse/SERVER-13735 . Basically a valid MultiPolygon is causing an error with the 2dsphere index on MongoDB 2.6.X. Others have reported similar issues so my bet is that it's a bug, or some undocumented limitation.

I'd vote up the issue on JIRA and add your voice to the comments - the more people let MongoDB know that this bug exists and is impacting them the faster it will get fixed.

Answer 2

The polygon is self-intersecting:

MongoDB prohibits such polygons.