Hi!

I have experienced some weird behavior (like missing items) when caching in spark after loading data from MongoDB. I have tried to replicate the problem with minimum code:

case class Item(name: String, value: Double)

// Loads collection with 10.000.000 items { name: String,  value: Number }
val imported = MongoSpark.load(sc, readConfig).toDS[Item]

val result = imported.cache

println(result.filter($"value" === 800).count())
// Prints 0!!!!!! (should be 1)

println(result.unpersist.filter($"value" === 800).count())
// Prints 1

I have tried the same loading the data from a file (same items exported using mongoexport) and it works fine, it always prints 1. That's why I think that the problem is related with MongoSpark and not Spark itself.

Thanks,
Alejandro.