我有以下系列:Mongoose mapReduce:減少返回對象或數組?
/* 0 */
{
"clientID" : ObjectId("51b9c10d91d1a3a52b0000b8"),
"_id" : ObjectId("532b4f1cb3d2eacb1300002b"),
"answers" : [],
"questions" : []
}
/* 1 */
{
"clientID" : ObjectId("51b9c10d91d1a3a52b0000b8"),
"_id" : ObjectId("532b6b9eb3d2eacb1300002c"),
"answers" : [
"1",
"8"
],
"questions" : [
"1",
"2",
"3"
]
}
/* 2 */
{
"clientID" : ObjectId("51b9c10d91d1a3a52b0000b8"),
"_id" : ObjectId("532b6baeb3d2eacb1300002d"),
"answers" : [
"1",
"8"
],
"questions" : [
"1",
"2",
"3"
]
}
/* 3 */
{
"clientID" : ObjectId("5335f9d864e2b1290c00012e"),
"_id" : ObjectId("533b828146ca43634000002d"),
"answers" : [
"ORANGE"
],
"questions" : [
"Color"
]
}
/* 4 */
{
"clientID" : ObjectId("5335f9d864e2b1290c00012e"),
"_id" : ObjectId("5351be327b539a4d1a00002b"),
"answers" : [
"ORANGE"
],
"questions" : [
"Color"
]
}
/* 5 */
{
"clientID" : ObjectId("5335f9d864e2b1290c00012e"),
"_id" : ObjectId("5351be5ec89d717d1a00002b"),
"answers" : [
"ORANGE"
],
"questions" : [
"Color"
]
}
我運行下面的代碼,以找到(問題,答案)組合出現了多少次集合中:
o.map= function(){
emit({"questions" : this.questions, "answers" :this.answers },this.clientID)
};
o.reduce = function(answers, collection){
return collection.length;
};
logSearchDB.mapReduce(o,function (err, results) {
results.sort(function(a, b){return b.value-a.value});
for (var i = 0; i < results.length; i++) {
console.log(JSON.stringify(results[i]))
};
})
的輸出是:
{"_id":{"questions":[],"answers":[]},"value":"51b9c10d91d1a3a52b0000b8"}
{"_id":{"questions":["Color"],"answers":["ORANGE"]},"value":3}
{"_id":{"questions":["1","2","3"],"answers":["1","8"]},"value":2}
我預計第一行將有「值」:1
我想'減少'功能得到'集合'對象:「51b9c10d91d1a3a52b0000b8」,而不是獲取數組:「[」51b9c10d91d1a3a52b0000b8「]。
爲什麼地圖縮小不會將所有內容都收集到數組中?