DZone
Thanks for visiting DZone today,
Edit Profile
  • Manage Email Subscriptions
  • How to Post to DZone
  • Article Submission Guidelines
Sign Out View Profile
  • Post an Article
  • Manage My Drafts
Over 2 million developers have joined DZone.
Log In / Join
Refcards Trend Reports Events Over 2 million developers have joined DZone. Join Today! Thanks for visiting DZone today,
Edit Profile Manage Email Subscriptions Moderation Admin Console How to Post to DZone Article Submission Guidelines
View Profile
Sign Out
Refcards
Trend Reports
Events
Zones
Culture and Methodologies Agile Career Development Methodologies Team Management
Data Engineering AI/ML Big Data Data Databases IoT
Software Design and Architecture Cloud Architecture Containers Integration Microservices Performance Security
Coding Frameworks Java JavaScript Languages Tools
Testing, Deployment, and Maintenance Deployment DevOps and CI/CD Maintenance Monitoring and Observability Testing, Tools, and Frameworks
Culture and Methodologies
Agile Career Development Methodologies Team Management
Data Engineering
AI/ML Big Data Data Databases IoT
Software Design and Architecture
Cloud Architecture Containers Integration Microservices Performance Security
Coding
Frameworks Java JavaScript Languages Tools
Testing, Deployment, and Maintenance
Deployment DevOps and CI/CD Maintenance Monitoring and Observability Testing, Tools, and Frameworks
  1. DZone
  2. Culture and Methodologies
  3. Agile
  4. Rob’s Sprint: Result Transformers

Rob’s Sprint: Result Transformers

Oren Eini user avatar by
Oren Eini
·
Mar. 08, 13 · Interview
Like (0)
Save
Tweet
Share
2.07K Views

Join the DZone community and get the full member experience.

Join For Free

By far the most confusing feature in RavenDB has been the index’s Transform Result. We introduced this feature to give the user the ability to do server side projections, including getting data from other documents.

Unfortunately, when we introduced this feature, we naturally added it to the index, and that cause a whole lot of confusion. In particular, people seemed to have a very hard time distinguishing between what get indexed and is searchable and the output of the index. To make matters worse, we also had major issues with how to determine the input of the TransformResults function. In short, the entire thing works, but from the point of view of an external user, that is really something that is very finicky and hard to get.

Instead, during Rob’s sprint, we have introduced a totally new concept. Stand-alone Result Transformers.

Here is what they look like:


public class OrdersStatsTransfromer : AbstractTransformerCreationTask<Order>
{
    public OrdersStatsTransfromer()
    {
        TransformResults = orders =>
                           from order in orders
                           select new
                           {
                               order.OrderedAt,
                               order.Status,
                               order.CustomerId,
                               CustomerName = LoadDocument<Customer>(order.CustomerId).Name,
                               LinesCount = order.Lines.Count
                           };
    }
}

And yes, they are quite intentionally modeled to be very similar to the way you would define them up to now, but outside of the index.

Now, why is that important? Because now you can apply a Transform Results on the server side without being tied to a customer.

For example, let us see how we can make use of this new feature:

var customerOrders = session.Query<Order>()
    .Where(x => x.CustomerId == "customers/123")
    .TransformWith<OrdersStatsTransfromer, OrderViewModel>()
    .ToList();

This separation between the result transformer and the index means that we can apply it to things like automatic indexes as well.

In fact, we can apply it during load:

var ovm = session.Load<OrdersStatsTransfromer, OrderViewModel>("orders/1");

There are a whole bunch of other goodies in there, as well. We made sure that now you don’t have to worry about the inputs to the transform. We will automatically use the right values when you access them, based on whatever you stored the field in the index or if it is accessible on the document.

All in all, this is a very major step forward, and it makes it drastically easier to use Result Transformers in various ways.




Sprint (software development)

Published at DZone with permission of Oren Eini, DZone MVB. See the original article here.

Opinions expressed by DZone contributors are their own.

Popular on DZone

  • Implementing Infinite Scroll in jOOQ
  • Cloud Native London Meetup: 3 Pitfalls Everyone Should Avoid With Cloud Data
  • The Importance of Delegation in Management Teams
  • Playwright vs. Cypress: The King Is Dead, Long Live the King?

Comments

Partner Resources

X

ABOUT US

  • About DZone
  • Send feedback
  • Careers
  • Sitemap

ADVERTISE

  • Advertise with DZone

CONTRIBUTE ON DZONE

  • Article Submission Guidelines
  • Become a Contributor
  • Visit the Writers' Zone

LEGAL

  • Terms of Service
  • Privacy Policy

CONTACT US

  • 600 Park Offices Drive
  • Suite 300
  • Durham, NC 27709
  • support@dzone.com
  • +1 (919) 678-0300

Let's be friends: