need get all key from object in mongodb

user_2779185 0
Viewed 606

I have data in following format

[
  { _id: ObjectId, spec: { abc: 'abc', bcd: 'bcd', cde: 'cde' } },
  { _id: ObjectId, spec: { bcd: 'bcd', cde: 'cde', efg: 'efg' } },
  { _id: ObjectId, spec: { cde: 'cde', efg: 'efg', ghi: 'ghi' } },
  { _id: ObjectId, spec: { ghi: 'ghi', abc: 'abc', bcd: 'bcd' } }
];

I need to get all keys from the spec object from all objects using aggregation like this.

['abc','bcd','cde','efg','ghi']
nosql-aggregation mongoose aggregation-framework mongodb
1 Answers
  • $objectToArray convert spec object to array in key-value format
  • $unwind deconstruct spec array
  • $group by null and construct the unique array of spec object's key using $addToSet
db.collection.aggregate([
  { $project: { spec: { $objectToArray: "$spec" } } },
  { $unwind: "$spec" },
  {
    $group: {
      _id: null,
      spec: { $addToSet: "$spec.k" }
    }
  }
])

Playground

user_89871280
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