Optimizing a RESTful Query in the client...

Question

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I have a RESTful service which wraps around the Entity Framework. Basically, all I did was create a database, add relations between the tables, create an Entity model around this database and finally expose the whole thing as a RESTful *.svc service. This is done, cannot be changed either.

Now I need to query data from it through a client application. All I can access is the service itself. I cannot add any server-side code, even if I wanted to. The server is now locked.

I need to retrieve data from a table called "ProductVoorwaarden" (product conditions) which is linked to three other tables. (Rubriek, Categorie and Datatype.) This data needs to be returned as XML, with a root node called "PRODUCTVOORWAARDEN" and every record in it's own XElement called "REC". Within this REC, there's an attribute for every field in the table plus references to related tables. Here's the code I have right now:

XElement PRODUCTVOORWAARDEN()
{
    XElement Result = new XElement("PRODUCTVOORWAARDEN");
    var Brondata = COBA.Productvoorwaarden.OrderBy(O => O.Code);
    foreach (var item in Brondata)
    {
        COBA.LoadProperty(item, "Rubriek");
        COBA.LoadProperty(item, "Categorie");
        COBA.LoadProperty(item, "Datatype");
        XElement REC = new XElement("REC",
            Attribute("Rubriek", item.Rubriek.Code),
            Attribute("Categorie", item.Categorie.Naam),
            Attribute("Code", item.Code),
            Attribute("Datatype", item.Datatype.Naam),
            Attribute("Eenheid", item.Eenheid),
            Attribute("Naam", item.Naam),
            Attribute("Omschrijving", item.Omschrijving),
            Attribute("UitgebreideTekstVeld", item.UitgebreideTekstVeld),
            Attribute("Veld", item.Veld)
        );
        Result.Add(REC);
    }
    return Result;
}

This code works fine, but it's slow. It reads all ProductVoorwaarden records but then it has to make round-trips to the server again for every record to retrieve Rubriek.Code, Categorie.Naam and Datatype.Naam. (In the database, these relations are set by an auto-incremental Identity field but the XML code uses Code or Naam as reference.)

As you can imagine, every trip back to the RESTful service just eats up more time, which I'm trying to avoid. So is there any way to speed this all up a bit more just on the client-side?

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The server is still under development and the next release will take a few more months. As a result, I have to deal with the options that the server provides right now. If there's no way to speed this up without modifying the server then fine. At least I've tried. There are 35 more tables that need to be processed with a deadline in a few days so if it works, then it works.

Answer 1

You could make each of your COBA.LoadProperty calls asynchronous and run them in parallel rather than sequentially. It will make your client code more complex since you'll have to handle the return of each async call and determine when they have all completed and you're ready to build your XML. Assuming each of your 4 REST calls is taking the same amount of time that would reduce the delay by half.

You've probably already double checked but I have come across cases where generating the enumerator from the lambda expression can be expensive. Still it was in the hundreds of milliseconds and I get the impression your delay is larger than that. May be worth checking.