node.js - Mongoose 映射减少()

Question

我正在跟踪玩家的分数以记录成长。我的架构如下:

Schema = new schema({
    pid: { type: Number }
  , name: { type: String }
  , alliance: {
      aid: { type: Number }
    , name: { type: String }
    }
  , city_cnt: { type: Number }
  , score: { type: Number }
  , rank: { type: Number }
  , createdTimeAt: { type: Date, default: Date.now }
  , createdDayAt: { type: Number, default: function() { return Math.floor(Date.now() / (24 * 60 * 60)) } }
})

现在我想为每个玩家每天提取一条记录(即当天最后记录的分数)。所以我有这个 map 缩小:

growthMap = function(){
  emit('createdTimeAt', this.createdTimeAt.toString())
}

growthReduce = function(prev, doc) { 
  if (doc.createdTimeAt > prev.createdTimeAt) {
    prev.createdTimeAt = doc.createdTimeAt
    prev.score = doc.score

    prev.pid = doc.pid
    prev.name = doc.name
  }
}

mongoose.connect('mongodb://localhost/my_database')
mongoose.model('Players', Schema)

mongoose.connection.db.executeDbCommand({
  mapreduce: 'players'
, map: growthMap.toString()
, reduce: growthReduce.toString()
, out: 'playerGrowth'
}, function(err, ret){ 
  if (err) console.log(err)
  else {
    console.log(ret.documents)
    mongoose.connection.db.collection('playerGrowths', function(err, collection){
      collection.find({}).toArray(function(err, docs){
        console.dir(docs)
      })

    })
  }
})

map 缩减似乎工作正常。第一个输出 console.log(ret.documents) 产生以下结果:

[ { result: 'playerGrowth',
    timeMillis: 11268,
    counts: { input: 14635, emit: 14635, reduce: 15, output: 1 },
    ok: 1 } ]

但是，每当我尝试在第二个输出 console.log(docs) 中查询新集合时，我都会得到一个空数组，没有任何结果。我确信我做错了什么，但是在涉及到 mapreduce 时缺少 mongoose 文档。

编辑

根据下面 Jed 的回答，我将 mongoose.connection.db.collection('playerGrowths' 更改为 mongoose.connection.db.collection('playerGrowth')，并且我至少从 find({}).toArray() 中得到了结果。但是，它仍然不是我所期望或需要的...

我的新结果

[ { result: 'playerGrowth',
    timeMillis: 5743,
    counts: { input: 14635, emit: 14635, reduce: 15, output: 1 },
    ok: 1 } ]
null
[ { _id: 'createdTimeAt', value: null } ]

Answer 1

尝试改变:

mongoose.connection.db.collection('playerGrowths'...

致:

mongoose.connection.db.collection('playerGrowth'...