MongoDB Error Code 16755 - Can't extract geo keys & duplicate vertices

When I try to create an index on geometry db.polygons.createIndex({"geometry":"2dsphere"}), it stops at a certain polygon with the error code 16755. It says it Can't extract geo keys and Duplicate vertices: 18 and 20.

So upon further inspection, it seems like this happens when 2 nodes in a polygon are close together, or even duplicates.

I then go manually remove this node in QGIS and re-try the process, only to find there's another polygon with the same issue.

How can I fix this issue without having to repeat the entire process of fixing polygon > uploading to MongoDB > creating index? Is there a way I can find out how many polygons have this issue?

2 Answers

I hit a similar problem. I just needed to find the valid records in my dataset (I discarded the records with Duplicate Vertices).

I renamed the collection -

db.myCollection.renameCollection('myCollectionBk') 

Then I added a single record from the original collection into a new collection and added a geospatial index to the collection

db.myCollection.insert(db.myCollectionBk.findOne()) // recreate the collection db.myCollection.createIndex({geometry:"2dsphere"}) // create the index (assumes the geometry on the record is valid) db.myCollection.remove({}) // remove the record 

Then I added the valid records into the new collection.

db.myCollectionBk.find().forEach(function(x){ db.myCollection.insert(x); }) 

Invalid records are simply ignored.

In your case you probably want to get the WriteResult from your insert, and look to see if it was successful. Something like

var errors = [] db.myCollectionBk.find().forEach(function(x){ var result = db.myCollection.insert(x); if (result.writeError) { errors.push({x._id:result.writeError.errmsg}); } }) 

As another alternative, check out this question (I couldn't get this to work)

So what I did was, I first created the collection with the index and then tried inserting using mongoimport which gave me how many were inserted successfully.

> db.someNewCollection.createIndex({"geometry":"2dsphere"}) 

To insert GeoJSON into MongoDB I did the following:

$ jq --compact-output ".features" yourGeoJSON > output.geojson $ mongoimport --db someDB -c someNewCollection --file "output.geojson" --jsonArray