Reverse array field in MongoDB

aggregation-framework, mongodb, mongodb-query

Solution

db.loc.find().forEach(function (doc) {
    var loc = [ doc.location[1], doc.location[0] ]; 
    db.loc.update(doc, { $set: { location: loc } });
})

Problem

I have a collection with a location field that was entered in the wrong order: ``` location: [38.7633698, -121.2697997] ``` When I try to place a 2d index on the field using ... ``` db.collection.ensureIndex({'location': '2d'}); ``` ... I get the following error because the latitude and longitude are reversed. ``` "err" : "location object expected, location array not in correct format", "code" : 13654 ``` How can I reverse this array for each document in the mongo shell?

Original source