Should I query on the server or on the client with BreezeJS?

I'm developing a SPA web application with Durandal and BreezeJS. On my server I have a BreezeAPI which returns my metadata, returns all data in a specific table lets say cars and which allows me to post my changes (SaveChanges).

Now lets get back to where I get all the cars with the method:

[HttpGet]
    public IQueryable<tblCar>AllCars()
    {
        return _contextProvider.Context.Car;
    }

I understand how I need to work with these but here is my question: Is it possible to query a specific car on the server? Or is this only possible on the client-side where I query over my fetched data from AllCars?

Solution

Just to clear, by default, all queries in Breeze are executed exclusively on the server. (You can query the local query cache but I don't think that is what you asking about.) What you can control is whether the query expression to be executed was defined exclusively on the server or is composed based on a query defined on the server along with additional client side restrictions.

If you want to define a query on the server that returns a single record you can certainly do so. It would look something like this:

[HttpGet]
public Car Car17()
{
    return _contextProvider.Context.Cars.First(c => c.CarId == 17);
}

which could be queried from the client via:

var q = EntityQuery.from("Car17");

Alternatively you could use query parameters:

[HttpGet]
public Car CarById(carId)
{
    return _contextProvider.Context.Cars.First(c => c.CarId == carId);
}

for which the query would look like this:

var q = EntityQuery.from("CarById").withParameters( { carId: 17} );

or you could do something like this:

[HttpGet]
public IQueryable<Car> AllCars()
{
    return _contextProvider.Context.Cars;
}

for which the query would look like this:

var q = EntityQuery.from("AllCars").where("CarId", "==", 17);

The important thing to be clear about is that all 3 of these execute exactly the same query on the server and return exactly the same results.

Hope this helps.