FAQ

Welcome to the mongolite wiki FAQ!

• How do I perform CRUD (Create, Read, Update, Delete) operations using an id field of mongodb’s ObjectId type? I.e. if your data in the database looks like:

  
  

  {
          "_id" : ObjectId("5566470bfec60042d1f186ac"),
          "something" : "Gravy",
          "something_else" : "Train",
          "flavor" : {},
  }

  
  When reading a document into R from mongolite an ObjectId is converted automatically into a character vector, but when you attempt to query the database using that character vector it doesn’t automatically convert it back to an ObjectId. The solution is to use the “$oid” operator:

  
  

  > m = mongo(db="test",collection="test")
  > DocId = "5566470bfec60042d1f186ac"
  > query = sprintf('{"_id":{"$oid":"%s"}}',DocId)
  > m$find(query)
   Imported 1 records. Simplifying into dataframe...
    something something_else flavor                  
  1     Gravy          Train   NULL
  > m$update(query,'{"$set":{"flavor":{"primary":"Chicken","seconday":"Beef"}}}')
  [1] TRUE
  > m$find(query)
   Imported 1 records. Simplifying into dataframe...
    something somethingelse flavor.primary flavor.secondary                  
  
  1     Gravy          Train        Chicken             Beef
  
  > m$remove(query)
  
  1 TRUE
  
  > m$find(query)
  
   Imported 0 records. Simplifying into dataframe…
  
  data frame with 0 columns and 0 rows