Get names in keys in MongoDB

1143040 pts.
Tags:
Big Data
MongoDB
I'm trying to get the names of all the keys in my MongoDB collection. Here's what I have so far:
db.things.insert( { type : ['dog', 'cat'] } );
db.things.insert( { egg : ['cat'] } );
db.things.insert( { type : [] } );
db.things.insert( { hello : []  } );
And I'm trying to get the unique keys, like so:
type, egg, hello
Thank you!
1

Answer Wiki

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Hi ITKE, 
You will do this with MapReduce:
mr = db.runCommand({
  “mapreduce” : “my_collection”,
  “map” : function() {
    for (var key in this) { emit(key, null); }
  },
  “reduce” : function(key, stuff) { return null; }, 
  “out”: “my_collection” + “_keys”
})
Then run distinct on the resulting collection so as to find all the keys:
db[mr.result].distinct(“_id”)
[“foo”, “bar”, “baz”, “_id”, …]
I hope it will assist you in resolving  your issues.
Thanks & Regards
Clark Kent

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