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Elements of Lens

The Lens is composed of elements such as fields, entities, dimensions, and measures. The objective of these elements is to define the structure and logic of data models. They introduce opinionated simplicity in explaining the reasoning for business concepts.

Entities

Entities are logical representations of an organization’s widely referred to and analyzed business concepts. They describe business objects such as customers, products, and users or business-specific activities such as web and app events, downloads, and purchases.

Apart from the name and description of an entity, entity declaration within a Lens defines the following properties.

Properties Description Requirement
SQL A query that runs against your data source to extract the entity table Mandatory
field Unique identifiers for an entity Optional
dimension Categorical or time-based data that helps in adding context to the measures Optional
measures Aggregated columns are calculated using SQL expressions. Measures are the foundation for defining metrics. Optional
relationship Defines the relationship of entities with other entities. An entity can be joined to other entities and have one-to-one, one-to-many, or many-to-one relationships. Optional
extend This allows you to extend an existing entity to use all declared elements of the entity. Optional

To learn more about entities, refer to Entity.

Field

Field, Dimensions, Measures, and Relationships are integral to the schema of all entities you define.

Fields are columns that uniquely identify an entity. The fields contain direct mapping to the underlying data source columns. Mention all the columns in the field that directly map to your underlying table.

Supported properties by fields

Properties Description Requirement
name Name of the field Optional
type Type of the field Mandatory
description Description of the field Optional
column Maps your field to the column in the physical table Optional
primary Use this property to explicitly state whether the field needs to be considered a primary key. Optional

To know more about fields, refer to Fields.

Dimensions

The Lens dimensions are columns containing qualitative data; they are groupable and can be used to query measures to varying levels of granularity.

Dimensions can be -

  • An attribute that can directly reference a column of the underlying table, or
  • A derived value calculated using a SQL expression

For instance, dimensions for a Customer entity might include first name, last name, email, phone, location, and age.

Supported properties for dimensions

Properties Description Mandatory/Optional
name Name of the dimension. Optional
description Description of the dimension. Optional
type Type of the dimension. Mandatory
sql_snippet A query to extract dimensions from the physical table. It can either be a one-to-one mapping to a column of your physical table, or you can define a custom query. Optional
sub_query Allows referencing measures from other entities. It’s of boolean type. Optional
hidden It will hide the dimension from the user interface if set to true. Optional

To know more about dimensions, refer to Dimensions.

Measures

Measures are aggregated numerical values derived from quantitative columns. You can also define complex expressions in the SQL snippet besides using the supported aggregation types. A measure can be referenced within a measure to achieve the desired aggregation.

For instance, Orders Entity might include measures such as quantities sold (count), total order amount(sum), and average order amount (avg).

Supported properties for measures

Properties Description Requirement
name Name of the measure Optional
description Description of the measure Optional
type Type of the measure. Yes
sql_snippet Based on the measure(aggregation) type, you can specify the aggregated column or define a custom query. Optional
rolling_window You can aggregate column values within a defined window, just like the SQL window function. Optional
hidden It will hide the dimension from the user interface if set to true. Optional

To know more about measures, refer to Measures.

Relationships

It defines the relationship between two entities; it can be - one-to-one, one-to-many, or many-to-one. A defined relationship simplifies querying dimensions and measures from multiple entities. Entities would be joined based on the defined keys and relationships. Once the relationship and fields are declared in the model, Lens will automatically generate join logic to render columns correctly.

Supported properties for relationships

Properties Sub-Property Description Requirement
field The field on which the join will be defined. Its ‘primary’ property is set to true (Primary Key) Mandatory
target Mandatory
name The entity you need to join.
field Join will be performed using this field of the entity
description Optional
type Type of the relationship - 1:1,1:N,N:1 Mandatory
sql_snippet If you have more than one clause in your join statement, you can add a query for it. Optional

To learn more about relationships, refer to Relationships.