组中两个嵌套数组mongodb的展开

Question

两种$unwind方法在NodeJS、MongoDb查询中可接受吗？我试着得到两个文档的所有不同的子文档。

以下是我的查询：

col.aggregate([
    {$match: {name: 'Facebook'}},

    {$unwind: "$products"},
    {$unwind: "$offices"},

    {$group:{
        "_id":  {
            CompanyName: "$name",
            HomepageURL: "$homepage_url",
            Description: "$description",
            NumberofEmployees: "$number_of_employees",
            TotalMoneyRaised: "$total_money_raised",
            FoundedYear: "$founded_year",
            CompanyCategory:{ $cond: { if: { $gte: [ "$number_of_employees", 10000 ] }, then: "BIG COMPANY", else: "SMALL COMPANY" }}    
                },
            Products: {$push: '$products.name'},             
            Offices: {$push: '$offices.description'}    
            }   
    },

    {$sort:{name: 1}}

]).toArray(function(err, docs) {
    console.log(docs);
    client.close();
});
});

我尝试展开两个嵌套数组，但查询输出重复值。这是Products和Offices的结果

Products:
 [ 'Facebook Platform',
   'Facebook Platform',
   'Facebook Platform',
   'Facebook News Feed',
   'Facebook News Feed',
   'Facebook News Feed',
   'Facebook Chat',
   'Facebook Chat',
   'Facebook Chat',
   'Facebook Connect',
   'Facebook Connect',
   'Facebook Connect',
   'Facebook Mobile',
   'Facebook Mobile',
   'Facebook Mobile',
   'Facebook',
   'Facebook',
   'Facebook',
   'Facebook Lite',
   'Facebook Lite',
   'Facebook Lite',
   'Facebook Places',
   'Facebook Places',
   'Facebook Places' ],
Offices:
 [ 'Headquarters',
   'Europe HQ',
   'New York',
   'Headquarters',
   'Europe HQ',
   'New York',
   'Headquarters',
   'Europe HQ',
   'New York',
   'Headquarters',
   'Europe HQ',
   'New York',
   'Headquarters',
   'Europe HQ',
   'New York',
   'Headquarters',
   'Europe HQ',
   'New York',
   'Headquarters',
   'Europe HQ',
   'New York',
   'Headquarters',
   'Europe HQ',
   'New York' ] } ]

这是我想要的结果，独特的产品和不同的办公室：

[ { _id:
 { CompanyName: 'Facebook',
   HomepageURL: 'http://facebook.com',
   Description: 'Social network',
   NumberofEmployees: 5299,
   TotalMoneyRaised: '$2.43B',
   FoundedYear: 2004,
   CompanyCategory: 'SMALL COMPANY' },
Products:
 [ 'Facebook Platform',
   'Facebook News Feed',
   'Facebook Chat',
   'Facebook Connect',
   'Facebook Mobile',
   'Facebook',
   'Facebook Lite',
   'Facebook Places'  ],
Offices:
 [ 'Headquarters',
   'Europe HQ',
   'New York'] } ]

以下是供参考的数据库：

 {
"_id" : ObjectId("52cdef7c4bab8bd675297d8e"),
"name" : "Facebook",
"homepage_url" : "http://facebook.com",
"description" : "Social network",
"number_of_employees" : 5299,
"total_money_raised" : "$2.43B",
"founded_year" : 2004,
"number_of_employees" : 5299,
"products" : [ 
    {
        "name" : "Facebook Platform",
        "permalink" : "facebook-platform"
    }, 
    {
        "name" : "Facebook News Feed",
        "permalink" : "facebook-news-feed"
    }, 
    {
        "name" : "Facebook Chat",
        "permalink" : "facebook-chat"
    }, 
    {
        "name" : "Facebook Connect",
        "permalink" : "facebook-connect"
    }, 
    {
        "name" : "Facebook Mobile",
        "permalink" : "facebook-iphone-app"
    }, 
    {
        "name" : "Facebook",
        "permalink" : "facebook-zero"
    }, 
    {
        "name" : "Facebook Lite",
        "permalink" : "facebook-lite"
    }, 
    {
        "name" : "Facebook Places",
        "permalink" : "facebook-places"
    }
],
"offices" : [ 
    {
        "description" : "Headquarters",
        "address1" : "1601 Willow Road",
        "address2" : "",
        "zip_code" : "94025",
        "city" : "Menlo Park",
        "state_code" : "CA",
        "country_code" : "USA",
        "latitude" : 37.41605,
        "longitude" : -122.151801
    }, 
    {
        "description" : "Europe HQ",
        "address1" : "",
        "address2" : "",
        "zip_code" : "",
        "city" : "Dublin",
        "state_code" : null,
        "country_code" : "IRL",
        "latitude" : 53.344104,
        "longitude" : -6.267494
    }, 
    {
        "description" : "New York",
        "address1" : "340 Madison Ave",
        "address2" : "",
        "zip_code" : "10017",
        "city" : "New York",
        "state_code" : "NY",
        "country_code" : "USA",
        "latitude" : 40.7557162,
        "longitude" : -73.9792469
    }
],

addtoset查询(w/o展开)：

    col.aggregate([
    {$match: {name: 'Facebook'}},

    //{$unwind: "$products"},
    //{$unwind: "$offices"},

    {$group:{
        "_id":  {
            CompanyName: "$name",
            HomepageURL: "$homepage_url",
            Description: "$description",
            NumberofEmployees: "$number_of_employees",
            TotalMoneyRaised: "$total_money_raised",
            FoundedYear: "$founded_year",
            CompanyCategory:{ $cond: { if: { $gte: [ "$number_of_employees", 10000 ] }, then: "BIG COMPANY", else: "SMALL COMPANY" }}    
            },
            Products: {$addtoset: '$products.name'},             
            //Offices: {$push: '$offices.description'}    
            }
    },

    {$sort:{name: 1}}

]).toArray(function(err, docs) {
    console.log(docs);
    client.close();
});

在使用addtoset时，解压o没有，空值结果也是相同的，使用解风推送是有效的(仅1 $unwind )

Answer 1

只需将组阶段中的2 $push替换为$addToSet：它只会“推”一次，而不需要征税。