Use publications or separate into collections (performance)?

Question

I have a collection, in which only two queries are ever called on it.

Ex. Cars.find({color: 'red'}); and Cars.find({color: 'blue'});

I was wondering if I should just create RedCars and BlueCars collections instead of using two publications on Cars .

Thinking of performance here, if the Cars collection were to get very large, would it be more performant to use two collections? Also, they are never called on the same template. Each has its own template.

Thanks

Answer 1

From a Mongo perspective, if you have a scenario where a single field across documents within a collection begins to look like an index (as you have described above) it will actually start to index queries against that field and make the return highly tuned. You can update this index (and if you have a lot of data that falls into scenario like you have described, you should tune this index), using standard Mongo indexing parameters against the database. There is more to this performance as well. For example, if it is a high read, low write, then Mongo will often keep portions or all of the query in memory for quick retrieval if it can.

As for whether it is better to split these into two collections. That's a tough one. From a performance standpoint it might be about the same either way if you tune your indexes properly and allow Mongo to do what it does best. However, from the meteor standpoint, I would consider it much easier to just keep them in a single collection from a code maintainability and testability standpoint.

Answer 2

In terms of performance, if the collection does get large, then your application will end up receiving alot more data than you expected it to if changes are made on either blue or red cars. A good solution rather than creating two collection is to use a parameterized subscription that will filter only on the data set you are looking at.

eg

    Meteor.publish('cars', function(c) {
        check(c, String);
        return Cars.find({color: c});
    });

Then you can access the data by subscribing Meteor.subscribe('cars', 'blue')