変数を使って配列の長さを取得しましたmongodb

Question

私はmongodbを初めて使っています。次のようなデータセットを持っています。個体を特定するユニークな企業の数を決定する集約クエリを作成しようとしています。関連付けられています。

スキーマ：

{ 
    "_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" : [ ] 

}

ここでは、私が試したクエリです：

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

私は今$relationships配列の長さを取得する必要があると思いますか？どうすればいい？

Answer 1

本当に配列のサイズが必要な場合は、巻き戻す必要はありません。 $sizeをそのまま使用してください。これは私の頭のouttaから私はあなたの凝集を変更するであろう、あなたが私はあなたが凝集のいくつかのより多くのロジックをしたい理解したコメントから

を望む結果を与える必要があり

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

： はにあなたの集計を変更します私は