Find all objects, that's nested properties have desired value - mongodb

Question

I have collection with the following (sample) documents:
{
"label": "Tree",
"properties": {
"height": {
"type": "int",
"label": "Height",
"description": "In meters"
},
"coordinates": {
"type": "coords",
"label": "Coordinates"
},
"age": {
"type": "int",
"label": "Age"
}
}
}
Keys in the properties attribute are different for almost each of the documents in collection.
I want to find all documents that have at least one property of given type.
What I'm looking for is to query this for {"properties.*.type": "coords"}. But this is not working as it is only my invention of mongo query.
Every help I was able to find concerned the $elemMatch operator which I can not use here because properties is an object, not an array.

Answer 1

Hi as per my knowledge in mongodb not provide this kind of search. So for finding this first I separated out all keys using map-reduce and then find query form so below code will help you
var mapReduce = db.runCommand({
"mapreduce": "collectionName",
"map": function() {
for (var key in this.properties) {
emit(key, null);
}
},
"reduce": function(key, stuff) {
return null;
},
"out": "collectionName" + "_keys"
})
db[mapReduce.result].distinct("_id").forEach(function(data) {
findkey = [];
findkey.push("properties." + data + ".type");
var query = {};
query[findkey] = "coords";
var myCursor = db.collectionName.find(query);
while (myCursor.hasNext()) {
print(tojson(myCursor.next()));
}
})

Answer 2

MongoDB doesn't support searches on keys - things like properties.* to match all subkeys of properties, etc. You shouldn't have arbitrary keys or keys that you don't know about in your schema, unless they are just for display, generally, because you will not be able to interact with them very easily in MongoDB.
If you do want to store dynamic attributes, the best approach is usually an array like the following:
{
"properties" : [
{
"key" : "height",
"value" : {
"type" : "Int",
"label" : "Height",
"description" : "In meters"
}
},
...
]
}
Efficient querying for your use case
find all documents that have at least one property of given type
results from an index on { "key" : 1 }:
db.test.find({ "properties.key" : { "$in" : ["height", "coordinates", "age"] } })