CODEWITHSUNDEEP
mongodbnosql
Alexio Cassani
Alexio Cassani

Reputation: 277

MongoDB: MapReduce ora Aggregation Framework for this kind of query?

I've the following documents in my collection:

{
  "attr_a" : {
        "_id" : ObjectId("51877b939a9cd88730d6030e"),
        "key" : "a-key-1",
        "name" : "a name 1"    
    },

    "attr_b" : {
          "_id" : ObjectId("51877b9392lfd88730d602sw"),
          "key" : "b-key-1",
          "name" : "b name 2"    
      }

}


{
  "attr_a" : {
        "_id" : ObjectId("51877b939a9cd88730d6030e"),
        "key" : "a-key-2",
        "name" : "a name 2"    
    },

  "attr_b" : {
        "_id" : ObjectId("51877b9392lfd88730d602sw"),
        "key" : "b-key-2",
        "name" : "b name 2"    
    }

}

And I want to create a query the produces as result something like:

{
  "attr_a" : [{
        "_id" : ObjectId("51877b939a9cd88730d6030e"),
        "key" : "a-key-1",
        "name" : "a name 1"    
    }, 
    {
          "_id" : ObjectId("51877b939a9cd88730d6030e"),
          "key" : "a-key-2",
          "name" : "a name 2"    
      }
    ],

"attr_b" : [{
      "_id" : ObjectId("51877b9392lfd88730d602sw"),
      "key" : "b-key-1",
      "name" : "b name 2"    
  }, 
  {
        "_id" : ObjectId("51877b9392lfd88730d602sw"),
        "key" : "b-key-2",
        "name" : "b name 2"    
  }]

}

I'm using MongoDB 2.6.x and Spring Data 1.6.5 and I'm trying to figure out if it can be done with the aggregation framework or with the map-reduce (in both case it should be done in real time) or in another different way.

Or should I take in consideration to introduce a Solr/Elastic Search?

Any suggestion?

Thanks in advance, Alexio Cassani

Upvotes: 0

Views: 144

Answers (1)

JohnnyHK
JohnnyHK

Reputation: 311865

You can do that by grouping the entire collection into a single doc, using $push to assemble the arrays:

db.test.aggregate([{$group: {
    _id: null, 
    attr_a: {$push: '$attr_a'},
    attr_b: {$push: '$attr_b'}
}}])

Upvotes: 1

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