casbahでupsertする際のObjectIdに関する謎挙動

.casbah-objectid-mystery.md

casbahでupsertする際のObjectIdに関する謎挙動

build.sbt

scalaVersion := "2.11.5"

libraryDependencies += "org.mongodb" % "casbah_2.11" % "2.8.0"

Test.scala

import com.mongodb.casbah.Imports._

object Test extends App {
  
  val username = "test"
  val password = "test"
  val host = "127.0.0.1"
  val port = 27017
  val database = "test"
  
  def connect(f: MongoDB => Unit) {
    val client = MongoClient(MongoClientURI(s"mongodb://$username:$password@$host:$port/$database"))
    try
      f(client(database))
    finally
      client.close
  }
  
  val failed = { db: MongoDB =>
    println("失敗するパターン")
    
    val coll = db("sample")
    
    coll.drop
    
    val id = new ObjectId
    
    val where = DBObject("_id" -> DBObject("$eq" -> id))
    val set = DBObject("_id" -> id)
    
    val result = coll.update(where, set, upsert=true)
    /* なぜ???
      com.mongodb.WriteConcernException
        serverUsed : "127.0.0.1:27017"
        ok : 1
        n : 0
        updatedExisting : false
        err : The _id field cannot be changed from {_id: { $eq: ObjectId('54fbcc2c3004a4267ff36eec') }} to {_id: ObjectId('54fbcc2c3004a4267ff36eec')}."
        code : 16836
    */
    println(result)
  }
  
  val success = { db: MongoDB =>
    println("成功するパターン")
    
    val coll = db("sample")
    
    coll.drop
    
    val id = new ObjectId
    
    val where = DBObject("_id" -> id) // <= 変更箇所
    val set = DBObject("_id" -> id)
    
    val result = coll.update(where, set, upsert=true)
    
    println(result)
  }
  
  //connect(success)
  connect(failed)
  
}