通過可變剛剛建立的MongoDB

Question

我是新來的MongoDB得到數組的長度，我有一個數據集看起來像下面，我試圖寫一個聚集查詢，將決定獨特的企業數量與個人已關聯。

模式：

{ 
    "_id" : ObjectId("52cdef7c4bab8bd675297d8b"), 
    "name" : "AdventNet", 
    "permalink" : "abc3", 
    "crunchbase_url" : "http://www.crunchbase.com/company/adventnet", 
    "homepage_url" : "http://adventnet.com", 
    "blog_url" : "", 
    "blog_feed_url" : "", 
    "twitter_username" : "manageengine", 
    "category_code" : "enterprise", 
    "number_of_employees" : 600, 
    "founded_year" : 1996, 
    "deadpooled_year" : 2, 
    "tag_list" : "", 
    "alias_list" : "Zoho ManageEngine ", 
    "email_address" : "pr@adventnet.com", 
    "phone_number" : "925-924-9500", 
    "description" : "Server Management Software", 
    "created_at" : ISODate("2007-05-25T19:24:22Z"), 
    "updated_at" : "Wed Oct 31 18:26:09 UTC 2012", 
    "overview" : "<p>AdventNet is now <a href=\"/company/zoho-manageengine\" title=\"Zoho ManageEngine\" rel=\"nofollow\">Zoho ManageEngine</a>.</p>\n\n<p>Founded in 1996, AdventNet has served a diverse range of enterprise IT, networking and telecom customers.</p>\n\n<p>AdventNet supplies server and network management software.</p>", 
    "image" : { 
     "available_sizes" : [ 
      [ 
       [ 
        150, 
        55 
       ], 
       "assets/images/resized/0001/9732/19732v1-max-150x150.png" 
      ], 
      [ 
       [ 
        150, 
        55 
       ], 
       "assets/images/resized/0001/9732/19732v1-max-250x250.png" 
      ], 
      [ 
       [ 
        150, 
        55 
       ], 
       "assets/images/resized/0001/9732/19732v1-max-450x450.png" 
      ] 
     ] 
    }, 
    "products" : [ ], 
    "relationships" : [ 
     { 
      "is_past" : true, 
      "title" : "CEO and Co-Founder", 
      "person" : { 
       "first_name" : "Sridhar", 
       "last_name" : "Vembu", 
       "permalink" : "sridhar-vembu" 
      } 
     }, 
     { 
      "is_past" : true, 
      "title" : "VP of Business Dev", 
      "person" : { 
       "first_name" : "Neil", 
       "last_name" : "Butani", 
       "permalink" : "neil-butani" 
      } 
     }, 
     { 
      "is_past" : true, 
      "title" : "Usabiliy Engineer", 
      "person" : { 
       "first_name" : "Bharath", 
       "last_name" : "Balasubramanian", 
       "permalink" : "bharath-balasibramanian" 
      } 
     }, 
     { 
      "is_past" : true, 
      "title" : "Director of Engineering", 
      "person" : { 
       "first_name" : "Rajendran", 
       "last_name" : "Dandapani", 
       "permalink" : "rajendran-dandapani" 
      } 
     }, 
     { 
      "is_past" : true, 
      "title" : "Market Analyst", 
      "person" : { 
       "first_name" : "Aravind", 
       "last_name" : "Natarajan", 
       "permalink" : "aravind-natarajan" 
      } 
     }, 
     { 
      "is_past" : true, 
      "title" : "Director of Product Management", 
      "person" : { 
       "first_name" : "Hyther", 
       "last_name" : "Nizam", 
       "permalink" : "hyther-nizam" 
      } 
     }, 
     { 
      "is_past" : true, 
      "title" : "Western Regional OEM Sales Manager", 
      "person" : { 
       "first_name" : "Ian", 
       "last_name" : "Wenig", 
       "permalink" : "ian-wenig" 
      } 
     } 
    ], 
    "competitions" : [ ], 
    "providerships" : [ 
     { 
      "title" : "DHFH", 
      "is_past" : true, 
      "provider" : { 
       "name" : "A Small Orange", 
       "permalink" : "a-small-orange" 
      } 
     } 
    ], 
    "total_money_raised" : "$0", 
    "funding_rounds" : [ ], 
    "investments" : [ ], 
    "acquisition" : null, 
    "acquisitions" : [ ], 
    "offices" : [ 
     { 
      "description" : "Headquarters", 
      "address1" : "4900 Hopyard Rd.", 
      "address2" : "Suite 310", 
      "zip_code" : "94588", 
      "city" : "Pleasanton", 
      "state_code" : "CA", 
      "country_code" : "USA", 
      "latitude" : 37.692934, 
      "longitude" : -121.904945 
     } 
    ], 
    "milestones" : [ ], 
    "video_embeds" : [ ], 
    "screenshots" : [ 
     { 
      "available_sizes" : [ 
       [ 
        [ 
         150, 
         94 
        ], 
        "assets/images/resized/0004/3400/43400v1-max-150x150.png" 
       ], 
       [ 
        [ 
         250, 
         156 
        ], 
        "assets/images/resized/0004/3400/43400v1-max-250x250.png" 
       ], 
       [ 
        [ 
         450, 
         282 
        ], 
        "assets/images/resized/0004/3400/43400v1-max-450x450.png" 
       ] 
      ], 
      "attribution" : null 
     } 
    ], 
    "external_links" : [ ], 
    "partners" : [ ] 

}

這裏是我試過的查詢：

 db.companies.aggregate([{ 
    $match: { 
    "relationships.person": { 
     $ne: null 
    } 
    } 
}, { 
    $project: { 
    relationships: 1, 
    _id: 0 
    } 
}, { 
    $unwind: "$relationships" 
}, { 
    $group: { 
    _id: "$relationships.person", 
    count: { 
     $addToSet: "$relationships" 
    } 
    } 
}]) 

我想我現在需要得到$relationships數組的長度？我會怎麼做？

Answer 1

當你只想要數組的大小，你真的不需要放鬆... 只需使用$size。 改變你聚集到：

db.companies.aggregate([{ 
    $match: { 
    "relationships.person": { 
     $ne: null 
    } 
    } 
}, { 
    $project: { 
    relationships: 1, 
    _id: 0, 
    relationship_size : { $size : "$relationships"} 
    } 
} 
}]) 

這應該給你你想要

從評論你想要更多的邏輯在聚集，從離開我的頭，我會改變你的聚集，我理解的結果：

db.companies.aggregate([{ 
    $match: { 
    "relationships.person": { 
     $ne: null 
    } 
    } 
}, { 
    $project: { 
    relationships: 1, 
    _id: 0 
    } 
}, { 
    $unwind: "$relationships" 
}, { 
    $group: { 
    _id: "$relationships.person.permalink", 
    count : {$sum : 1} 
    } 
}]) 

我不能在你的人際關係陣列找到一個「公司名稱」，所以我用的是永久屬性