Node プログラムで mongodb の集計メソッドを使用しようとすると、型エラーが発生します。ノード 0.10.16 バージョンと mongodb mongodb-win32-x86_64-2.4.2 バージョンを使用しています。
mongodb の「関係」テーブルの詳細は次のとおりです。
db.relation.find().forEach(printjson)
{ "_id" : ObjectId("518808811189128048034c7b") }
{
"username" : "51880fa37901642c36000001",
"selectedoption" : "RCB",
"question" : "Which team is going to win IPL6?",
"_id" : ObjectId("5188137dee3a599c34000001")
}
{
"username" : "51880fa37901642c36000001",
"selectedoption" : "Mumbai",
"question" : "Which team is going to win IPL6?",
"_id" : ObjectId("518c2bd0afa8d2e82b000001")
}
{
"username" : "51880fa37901642c36000001",
"selectedoption" : "Mumbai",
"question" : "Which team is going to win IPL6?",
"_id" : ObjectId("518c2c81681aae0838000001")
}
{
"username" : "51880fa37901642c36000001",
"selectedoption" : "RCB",
"question" : "Which team is going to win IPL6?",
"_id" : ObjectId("518c2c90681aae0838000002")
}
{
"username" : "51880fa37901642c36000001",
"selectedoption" : "CSK",
"question" : "Which team is going to win IPL6?",
"_id" : ObjectId("518c2cefc7dc797c08000001")
}
{
"username" : "51880fa37901642c36000001",
"selectedoption" : "Mumbai",
"question" : "Which team is going to win IPL6?",
"_id" : ObjectId("518c2d48a2afbdc426000001")
}
{
"username" : "51880fa37901642c36000001",
"selectedoption" : "RCB",
"question" : "Which team is going to win IPL6?",
"_id" : ObjectId("518c2e2fa2afbdc426000002")
}
{
"username" : "521fda91a6abb63037000001",
"selectedoption" : "RCB",
"question" : "Which team is going to win IPL6?",
"_id" : ObjectId("521fda9ea6abb63037000002")
}
{
"username" : "521fda91a6abb63037000001",
"selectedoption" : "CSK",
"question" : "who will IPL this year?",
"_id" : ObjectId("521fdb3ba6abb63037000003")
}
{
"username" : "521fda91a6abb63037000001",
"selectedoption" : "Mumbai",
"question" : "Which team is going to win IPL6?",
"_id" : ObjectId("521fde8da6abb63037000004")
}
{
"username" : "521fda91a6abb63037000001",
"selectedoption" : "CSK",
"question" : "who will IPL this year?",
"_id" : ObjectId("521fdef0a6abb63037000005")
}
{
"username" : "521fda91a6abb63037000001",
"selectedoption" : "Mumbai",
"question" : "Which team is going to win IPL6?",
"_id" : ObjectId("521fdf1aa6abb63037000006")
}
{
"username" : "521fda91a6abb63037000001",
"selectedoption" : "RCB",
"question" : "Which team is going to win IPL6?",
"_id" : ObjectId("521fdffe257b59cc3f000001")
}
{
"username" : "521fda91a6abb63037000001",
"selectedoption" : "Mumbai",
"question" : "Which team is going to win IPL6?",
"_id" : ObjectId("521fe09c827ff1e418000001")
}
{
"username" : "521fda91a6abb63037000001",
"selectedoption" : "CSK",
"question" : "Which team is going to win IPL6?",
"_id" : ObjectId("521fe0cb5022f0c03c000001")
}
{
"username" : "521fda91a6abb63037000001",
"selectedoption" : "Mumbai",
"question" : "Which team is going to win IPL6?",
"_id" : ObjectId("521fe1558b82555c25000001")
}
{
"username" : "521fda91a6abb63037000001",
"selectedoption" : "CSK",
"question" : "Which team is going to win IPL6?",
"_id" : ObjectId("521fe17d8b82555c25000002")
}
{
"username" : "521fda91a6abb63037000001",
"selectedoption" : "CSK",
"question" : "Which team is going to win IPL6?",
"_id" : ObjectId("521fe2e8c134b7bc40000001")
}
{
"username" : "521fda91a6abb63037000001",
"selectedoption" : "CSK",
"question" : "who will IPL this year?",
"_id" : ObjectId("521fe354b59421cc07000001")
}
{
"username" : "521fda91a6abb63037000001",
"selectedoption" : "RCB",
"question" : "Which team is going to win IPL6?",
"_id" : ObjectId("521fe392b59421cc07000002")
}
これはすべて上記の表の大まかなデータです (mongodb のコレクション)。「selectedoption」列に基づいて、上記の表のSQL用語で「group by」が必要であり、それをカウントするだけです。したがって、結果は「RCB」、「CSK」、「ムンバイ」データのカウントになります。これが私のサンプルノードスニペットで、不要な行を削除しました。エクスプレスサーバーを使用しています-
var express = require('express'),
routes = require('./routes'),
user = require('./routes/user'),
http = require('http'),
path = require('path');
var app = express();
var mongo = require('mongodb');
var db = new mongo.Db('voteapp', new mongo.Server("127.0.0.1", 27017, {
auto_reconnect: true
}, {
safe: false,
strict: false
}))
app.get('/test', function(req, res) {
res.send('works');
db.collection('relation', function(err, collection){
console.log('in');
collection.aggregate({$group : {_id: "$selectedoption", selectedoption: {$sum: 1}}});
console.log('out');
});
});
上記の行 -
collection.aggregate({$group : {_id: "$selectedoption", selectedoption: {$sum: 1}}})
ノードコンソールに次のエラーが表示されます
TypeError: Collection.aggregate で未定義のプロパティ 'readPreference' を読み取れません(D:\mongo-js - 1\node_modules\mongodb\lib\mongodb\collection.js:1632:17)
at D:\mongo-js - 1\app.js:107:16 at Db.collection (D:\mongo-js - 1\node_modules\mongodb\lib\mongodb\db.js:461:44) at D:\mongo-js - 1\app.js:105:6 at callbacks (D:\mongo-js - 1\node_modules\express\lib\router\index.js:161:37) at param (D:\mongo-js - 1\node_modules\express\lib\router\index.js:135:11) at pass (D:\mongo-js - 1\node_modules\express\lib\router\index.js:142:5) at Router._dispatch (D:\mongo-js - 1\node_modules\express\lib\router\index.js:170:5) at Object.router (D:\mongo-js - 1\node_modules\express\lib\router\index.js:33:10) at next (D:\mongo-js - 1\node_modules\express\node_modules\connect\lib\proto.js:190:15)
- mongodb コンソールで正常に動作し、次の出力が得られます -
> db.relation.aggregate({$group : {_id: "$selectedoption", selectedoption: {$sum: 1}}});
{
"result" : [
{
"_id" : "CSK",
"selectedoption" : 9
},
{
"_id" : "Mumbai",
"selectedoption" : 10
},
{
"_id" : "RCB",
"selectedoption" : 8
},
{
"_id" : null,
"selectedoption" : 1
}
],
"ok" : 1
}
この問題を解決するための指針やガイダンスをいただければ幸いです。