基於第三級嵌套字段檢索文檔

Question

我是mongodb的新手，我需要檢索任何座標值爲空或空的文檔。 例如座標[0]或座標[1]爲空。

{ 
"_id": ObjectId("58ef15dcccac183a18cd5c69"), 
"submission_location": { 
    "type": "Point", 
    "coordinates": [73.0574529, 
    33.711476] 
}} 


{ 
"_id": ObjectId("58ef1acaccac183918cd5c6a"), 
"submission_location": { 
    "type": "Point", 
    "coordinates": [] 
}} 

我已經使用了聚合方法，但它沒有返回任何結果。

db.tasks_submission.aggregate([ 
    { 
    "$unwind": "$submission_location" 
    }, 
    { 
    "$unwind": "$submission_location.coordinates.0", 
    "$unwind": "$submission_location.coordinates.1" 
    }, 
    { 
    "$match": { 
     $or :[{ 
     "submission_location.coordinates.0": 0 
     }, 
     { 
     "submission_location.coordinates.1": 0 
     }] 

    } 
} 
]).pretty() 

Answer 1

https://docs.mongodb.com/v3.2/tutorial/query-for-null-fields/

可能是：

db.tasks_submission.find($or:[ 
    { submission_location.coordinates: null }, 
    { submission_location.coordinates.0: null }, 
    { submission_location.coordinates.1: null } 
])