Code Reusability: Extending Explores and Views (3.24+)

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Release 3.24 will come with the ability to extend Explores and Views. These are key features in building reusable models.

Building extensions is a pretty advanced topic. In order to understand how this works, you will first need to understand LookML’s facilities for naming explores, views and fields. Take a moment to review this, even if you are familiar with it. The subtleties are important.

Labeling, field naming and explore naming LookML

LookML gives you control over the the ways that fields are named, labeled, referenced, and expressed in the URL. By default all of these elements are identical, but in some cases (such as building reusable models) it may become important to modify how this naming occurs. Default Behavior - explore: order joins: - join: user sql_on: ${order.user_id} = ${user.id} relationship: many_to_one - view: order fields: - dimension: id - view: user fields: - dimension: id Appea…

LookML is implemented as an array of hashes in YAML. Each LookML Object (explore, view, field, join, dashboard, or dashboard element) is a named hash. LookML’s extensions are a mechanism for deeply copying and merging these objects.

Extending Explores and Views in an Existing Model

A design goal for extensions is that you can put all your extensions into a new separate file so that if the original model changes, you get all of the changes. Additionally, all the logic surrounding the extension is on one place. For example, a rolling average extension includes the explore, view and field definitions as well as dashboard that displays rolling averages. Simply drop the file into your model and change the name of the explore being extended.

Example

Assume the base e-commerce model:

Notice that the view: parameter is set in the explore. The view to use in an explore is by default the same name as the explore. Setting the view: allows the explore to be extended without having to set this parameter (this will likely be automatically set by the generator in the future).

- explore: orders
  view: orders
  joins:
    - join: users
      foreign_key: orders.user_id

    - join: order_items
      sql_on: ${order_items.order_id} = ${orders.id}
      relationship: one_to_many
      
    - join: inventory_items
      foreign_key: order_items.inventory_item_id

    - join: products
      foreign_key: inventory_items.product_id

Extending a joined view within an Explore.

Suppose the original model doesn’t have much in the way of age analysis. We can extend the model by simply creating a file with our extensions.

Extending a view within an explore happens in two steps:

1. Create a new view that has the desired fields to extend the original view. In this case, we extend users.
2. Create a new explore that extends orders, change the view for users by declaring the from: parameter. Notice that the linkage for users was copied from the join in the original orders view.

- explore: orders_with_age_extensions
  extends: orders
  joins:
  - join: users
    from: users_with_age_extensions
    
    
- view: users_with_age_extensions
  extends: users
  fields:
  - measure: average_age
    type: average
    sql: ${age}
    
  - dimension: age_tiers
    type: tier
    style: integer
    tiers: [10,20,30,50,70]
    sql: ${age}
  sets:
    detail: [SUPER*, age]

Example Extending just the Base View

There are 4 names associated with an explore. Its name in the UI (label:), its name in the url (explore:), the view that it is built from (from:), and the alias to use in the sql query and to prefix fields with (view:). It is important to understand each of these use cases. When extending a view, you usually want to change most of these.

- explore: better_orders
  extends: orders
  view: orders              
  from: orders_extended

- view: orders_extended
  extends: orders
  fields:
  - measure: count_in_california
    type: count
    filters:
      users.state: California

Play with it.

There is additional information about how this will work on learnbeta. Chat with a looker support analyst if you would like to play and don’t have an account.

Comment on it.

We’d love to hear your feedback. Let us know how you’re using the feature, what else you’d like to do with it, or anything else you think we should know.