Querying an entire specific array inside another array in mongoDB

Question

I have a mongoDB collection, called myCollection, and inside myCollection there is a structure like this:

{
    "id": 1234,
    "posts": [
       [
          {
             "id": "0.0",
             "name": "john",
             "message": "hello"
          },
          {
             "id": "0.1",
             "name": "jane",
             "message": "good morning"
          },
          {
             "id": "0.2",
             "name": "josh",
             "message": "good evening"
          }
       ],
       [
          {
             "id": "1.0",
             "name": "mark",
             "message": "good lunch"
          }
       ],
       [
          {
             "id": "2.0",
             "name": "john",
             "message": "bye bye"
          },
          {
             "id": "2.1",
             "name": "mark",
             "message": "hi"
          }
       ]
    ]
}

Can anyone tell me how I can query this structure to obtain the ENTIRE array that contains a specific object? For example, launching a query around this specific object:

{
    "id": "2.0",
    "name": "john",
    "message": "bye bye"
}

I would to obtain this entire array:

       [
          {
             "id": "2.0",
             "name": "john",
             "message": "bye bye"
          },
          {
             "id": "2.1",
             "name": "mark",
             "message": "hi"
          }
       ]

the_mahasagar · Accepted Answer · 2019-06-08 09:02:56Z

1

Hope below query is help :

db.myCollection.aggregate([
  { $match : { "id": 1234}},
  { $unwind  : '$posts'},
  {$match : {
        'posts' : { $elemMatch : { 'id' : '2.0',name : 'john'}} 
     }
  },
  { $unwind : '$posts'},
  { $project : {
      'id' : '$posts.id',
      name : '$posts.name',
      message :'$posts.message',
      _id : 0
     }
  }
])

edited Jun 8, 2019 at 9:02

answered Jun 8, 2019 at 1:44

the_mahasagar

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5 Comments

FedeLanza Over a year ago

thank you for your reply! myCollection also contains other documents besides the one with "id":"1234". So, how can I specify inside the query that you have suggested me that I want to search the array that contains the { 'id' : '2.0',name : 'john'} object only inside the document with "id":"1234"?

the_mahasagar Over a year ago

Answer Updated! check if you are passing "1234" or 1234.

FedeLanza Over a year ago

thank you so much for your answer. Unfortunately it doesn't work .. :( The query does not return the array [ { "id": "2.0", "name": "john", "message": "bye bye" }, { "id": "2.1", "name": "mark", "message": "hi" } ] ..... :(

FedeLanza Over a year ago

In particular, with the query that you have suggested me, I retrive the whole structure inside the collection. Can you tell me how I can get only the entire array [ { "id": "2.0", "name": "john", "message": "bye bye" }, { "id": "2.1", "name": "mark", "message": "hi" } ] ?

FedeLanza Over a year ago

Thank you very much @the_mahasagar for you help. Your solution works correctly and is exactly what I needed!

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