Mongo C-Driver: Insert element into nested array

Good Morning,

I am pretty new to MongoDB and using the c-driver so this question may seem trivial to some, but I am at a complete loss.

I have a document that has an array called 'folders' and inside each element of folders is a secondary array titled 'files'. I wish to add an entry into 'files' for a specific folder's array.

I have tried to create a BCON using $push in c, but I know I have completely screwed it all up. I get no compilation errors and I can run the application, but nothing happens to the document. I think my application aborts right at the time of this code because there is a printf just after it that fails to print, but if I remove the 'update = ' and 'mongoc_collection_update' lines from the code everything executes correctly. So I think my problem is the actual bcon structure is wrong and causing a fault on exec.

Sample Document

{ 
"_id" : ObjectId("5627e20d4bacefccf4864e4e"), 
"allow_save" : "true", 
"allow_add" : "true", 
"auto_approve_invites" : "true", 
"folders" : [
    {
        "folder_id" : "root", 
        "display_name" : "My Folder", 
        "files" : [
            {
                "modified" : "", 
                "file" : "58656607-801b-40e4-aa34-e01ef1def85b"
            }, 
            {
                "modified" : "", 
                "file" : "58656607-801b-40e4-aa34-e01ef1def85b"
            }, 
            {
                "modified" : "", 
                "file" : "58656607-801b-40e4-aa34-e01ef1def85b"
            }
        ]
    }, 
    {
        "folder_id" : "1", 
        "display_name" : "My Other Folder", 
        "preview_thumbnail" : "58656607-801b-40e4-aa34-e01ef1def85b", 
        "files" : [
            {
                "modified" : "", 
                "file" : "58656607-801b-40e4-aa34-e01ef1def85b"
            }, 
            {
                "modified" : "", 
                "file" : "58656607-801b-40e4-aa34-e01ef1def85b"
            }, 
            {
                "modified" : "", 
                "file" : "58656607-801b-40e4-aa34-e01ef1def85b"
            }
        ]
    }
]
}

Code Sample

collection = mongoc_client_get_collection (client, "***", "***");

update = bson_new ();
bson_oid_t oid;
bson_oid_init_from_string (&oid, tribe_id);
update = BCON_NEW ("_id", BCON_OID(&oid));

// Find the document
cursor = mongoc_collection_find (collection, MONGOC_QUERY_NONE, 0, 0, 0, query, NULL, NULL);

// add new file
update = BCON_NEW ("$push", 
        "{","folders.folder_id", BCON_UTF8 ("root"), "}",
        "{","new_file", "new value", "}");

mongoc_collection_update (collection, MONGOC_UPDATE_NONE, query, update, NULL, &error);