how to query for exact mach in unknown number of subfields in mongodb - mongodb

Question

I have a collection where documents can have an unknown number of sub documents:
"agent_id": {
"0":"1234",
"1":"2234",...etc
How do I search for an exact match in all the agent_id sub-fields?

Answer 1

You need to dynamically create an object with properties that are a concatenation of the embedded document name agent_id with the dot (.) and the field name, enclosed in quotes, something like this:
var query = {
"agent_id.0": "78343",
"agent_id.1": "78343",
"agent_id.2": "78343",
"agent_id.3": "78343",
...
"agent_id.n": "78343"
}
One way to create the object is generate the sub-documents keys with mapReduce. The following demonstrates this approach. In the Map-Reduce operation, an array of keys in the agent_id subdocument is generated to an output collection "collection_keys" and then used to produce the find() query expression:
Suppose you populate a sample collection
db.collection.insert([
{
"agent_id": {
"0":"1234",
"1":"2234",
"56":"8451",
"74":"1475",
"10":"1234"
}
},
{
"agent_id": {
"5":"5874",
"18":"2351"
}
}
])
Running the following mapReduce operation
var mr = db.runCommand({
"mapreduce" : "collection",
"map" : function() {
for (var key in this.agent_id) { emit(key, null); }
},
"reduce" : function(key, stuff) {
return null
},
"out": "collection" + "_keys"
});
var query = { "$or": [] },
value = "1234";
db[mr.result].distinct("_id").forEach(function (key){
var obj = {};
obj["agent_id." + key] = value;
query["$or"].push(obj)
});
printjson(query);
will produce:
{
"$or" : [
{
"agent_id.0" : "1234"
},
{
"agent_id.1" : "1234"
},
{
"agent_id.10" : "1234"
},
{
"agent_id.18" : "1234"
},
{
"agent_id.5" : "1234"
},
{
"agent_id.56" : "1234"
},
{
"agent_id.74" : "1234"
}
]
})
You can then use the query document in your find() query:
db.collection.find(query)
which will produce the result:
/* 0 */
{
"_id" : ObjectId("561d5312cd05efc95a1ea1f4"),
"agent_id" : {
"0" : "1234",
"1" : "2234",
"56" : "8451",
"74" : "1475",
"10" : "1234"
}
}