MongoSpark - convert bson Document to Map[String, Double]

Question

In my MongoDB database I have a collection of the following documents:

As one can see, each document has some nested documents (Decade, Title, Plot, Genres, etc.). Those are kinda Map representations of SparseVectors that I came up with. And are actually generated with my other Spark job.

As it appeared, these kinds of documents can't be easily read into the Spark DataFrame.

I was thinking how I can actually read such Documents into a Dataframe where each subdocument will be represented not by a bson Document but by a simple Map[String, Double]. Because each of those subdocuments is absolutely arbitrary and contains arbitrary number of numeric fields.

Is there a way to deal with such documents?

score 0 · Accepted Answer · answered Mar 20 '18 at 23:45

Managed to solve it. Here's how:

import spark.implicits._
final case class MovieData(imdbID: Int,
                       Title: Map[Int, Double],
                       Decade: Map[Int, Double],
                       Plot: Map[Int, Double],
                       Genres: Map[Int, Double],
                       Actors: Map[Int, Double],
                       Countries: Map[Int, Double],
                       Writers: Map[Int, Double],
                       Directors: Map[Int, Double],
                       Productions: Map[Int, Double]
                      )

val movieDataDf = MongoSpark
  .load(sc, moviesDataConfig).rdd.map((doc: Document) => {
    MovieData(
      doc.get("imdbID").asInstanceOf[Int],
      documentToMap(doc.get("Title").asInstanceOf[Document]),
      documentToMap(doc.get("Decade").asInstanceOf[Document]),
      documentToMap(doc.get("Plot").asInstanceOf[Document]),
      documentToMap(doc.get("Genres").asInstanceOf[Document]),
      documentToMap(doc.get("Actors").asInstanceOf[Document]),
      documentToMap(doc.get("Countries").asInstanceOf[Document]),
      documentToMap(doc.get("Writers").asInstanceOf[Document]),
      documentToMap(doc.get("Directors").asInstanceOf[Document]),
      documentToMap(doc.get("Productions").asInstanceOf[Document])
    )
}).toDF()

def documentToMap(doc: Document): Map[Int, Double] = {
  doc.keySet().toArray.map(key => {
    (key.toString.toInt, doc.getDouble(key).toDouble)
  }).toMap
}

Hopefully the code is self-explanatory. Some type casting and conversions did the job. Probably, not the most elegant solution though.

MongoSpark - convert bson Document to Map[String, Double]

1 Answers1