Querying a map (<String, Object>) in JSON through MongoDB - mongodb

Question

How to query a map of type Map<String, List> in JSON form, in MongoDB?
Sample JSON:
{
"WIDTH": 810,
"HEIGHT": 465,
"MODULES": {
"23": {
"XNAME": "COMP1",
"PARAMS": {
"_Klockers": {
"TYPE": "text",
"VALUE": "Klocker#3"
},
"SUBSYS": {
"TYPE": "text",
"VALUE": "2"
},
"EP": {
"TYPE": "integer",
"VALUE": "2"
}
}
},
"24": {
"XNAME": "COMP2",
"PARAMS": {
"_Rockers": {
"TYPE": "text",
"VALUE": "Rocker#3"
},
"Driver": {
"TYPE": "binary",
"VALUE": 1
},
"EP": {
"TYPE": "long",
"VALUE": "233"
}
}
},
"25": {
"XNAME": "COMP3",
"PARAMS": {
"_Mockers": {
"TYPE": "text",
"VALUE": "Mocker#3"
},
"SYSMain": {
"TYPE": "text",
"VALUE": "2342"
},
"TLP": {
"TYPE": "double",
"VALUE": "2.3"
}
}
}
}
}
Basically I want to :
List all the "XNAME" field values of all keys in "MODULES".
Expected output : {"COMP1", "COMP2", "COMP3"}
List all the "TYPE" in "PARAMS" object within each key of "MODULES".
Expected output : {"text", "text", "integer", "text", "binary", "long", "text", "text", "double"}
I am new to MongoDB and any help or redirection is appreciated.

Answer 1

You can use this
db.collection.aggregate([
{
$project: {//You require this as your data is dynamic
"modules": {
"$objectToArray": "$MODULES"
}
}
},
{//Destruct the array
"$unwind": "$modules"
},
{
"$project": {//Again, requires the same as keys are dynamic
"types": {
"$objectToArray": "$modules.v.PARAMS"
},
xname: "$modules.v.XNAME"
}
},
{//Destruct the types
$unwind: "$types"
},
{//Get the distinct values
$group: {
"_id": null,
"xname": {
"$addToSet": "$xname"
},
"types": {
"$addToSet": "$types.v.TYPE"
},
}
}
])