尝试在我的 Node 程序中使用 mongodb 的聚合方法时出现类型错误。我使用的是节点 0.10.16 版本和 mongodb mongodb-win32-x86_64-2.4.2 版本。
这是我在 mongodb 中的“关系”表的详细信息 - `
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")
}
这是上表中的所有粗略数据（在 mongodb 中收集）。我需要基于 'selectedoption' 列在上表中的 sql 术语中的 'group by'，只需要计算一下即可。所以结果将是对“RCB”、“CSK”、“Mumbai”数据的计数。这是我的示例节点片段，删除了不需要的行，我正在使用快速服务器 -
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: {$sum: 1}}});
console.log('out');
});
});
上一行 -
collection.aggregate({$group : {_id: "$selectedoption", selectedoption: {$sum: 1}}})
在节点控制台中给我以下错误
TypeError：无法读取 Collection.aggregate 处未定义的属性“readPreference”（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)
- 它在 mongodb 控制台中运行良好并给我以下输出 -
> 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
}
我非常感谢任何解决此问题的指示或指导。