Mongoose - recursive query (merge from multiple results)

Question

I have the following generic schema to represent different types of information.

var Record = new Schema (
{
   type: {type: String}, // any string (foo, bar, foobar)
   value: {type: String}, // any string value
   o_id: {type:String}
}
);

Some of the records based on this schema have:

• type="car"
• value="ferrari" or
• value="ford"

Some records have type "topspeed" with value "210" but they always share o_id (eg related "ferrari has this topspeed"). So if "ferrari has top speed 300", then both records have same o_id.

How can I make query to find "ferrari with topspeed 300" when I don't know o_id?

The only solution I found out is to select cars "ferrari" first and then with knowledge of all o_id for all "ferrari" use it to find topspeed.

In pseudocode:

Record.find({type:"car", value:"ferrari"}, function(err, docs)
{
   var condition = [];// create array of all found o_id;
   Record.find({type:"topspeed", value:"300"}...
}

I know that some merging or joining might not be possible, but what about some chaining these conditions to avoid recursion?

EDIT: Better example:

• Lets imagine I have a HTML document that contains DIV elements with certain id (o_id).

• Now each div element can contain different type of microdata items (Car, Animal...).

• Each microdata item has different properties ("topspeed", "numberOfLegs"...) based on the type (Car has a topspeed, animal numberOfLegs)

• Each property has some value (310 kph, 4 legs)

Now I'm saving these microdata items to the database but in a general way, agnostic of the type and values they contain since the user can define custom schemas from Car, to Animal, to pretty much anything). For that I defined the Record schema: type consists of "itemtype_propertyname" and value is value of the property.

I would eventually like to query "Give me o_id(s) of all DIV elements that contain item Ferrari and item Dog " at the same time.

The reason for this general approach is to allow anyone the ability to define custom schema and corresponding parser that stores the values.

But I will have only one search engine to find all different schemas and value combinations that will treat all possible schemas as a single definition.

Answer 1

I think it'd be far better to combine all records that share an o_id into a single record. Eg:

{
  _id: ObjectId(...),
  car: "ferarri",
  topspeed: 300
}

Then you won't have this problem, and your schema will be more efficient both in speed and storage size. This is how MongoDB is intended to be used -- heterogenous data can be stored in a single collection, because MongoDB is schemaless. If you continue with your current design, then no, there's no way to avoid multiple round-trips to the database.