MAP data type

Syntax for MAP

column_name MAP < primitive_type, type >
type ::= primitive_type | complex_type

MAP data types represent sets of key-value pairs. These collections have an arbitrary number of elements, where each element is the same type. A MAP type is like a miniature table; the table equivalent of a scalar (primitive) values that has two columns:

• KEY

  A scalar type, such as BIGINT, STRING, TIMESTAMP, which enables you to define non-continuous sequences or categories with arbitrary names. The keys in a map column may represent a numeric sequence of events during a manufacturing process, or TIMESTAMP values that correspond to sensor observations.

  Access as map_name.key.

• VALUE

  The second part of a key-value pair in a map. May be a scalar, or another complex type (an ARRAY, a STRUCT, or another MAP).

  Access as map_name.value.

  If a map contains a STRUCT, access as map_name.value.field_name, or as map_name.field_name.

MAPs in the Dataset Field Interface

In the Dataset Fields interface, an example of a basic MAP data type may look something like the following image. Notice that each level of a complex data type may be expanded to show component details, or collapsed.

In the example of the dataset Complex Type - Map, you can see that the Dimension Customer (a String, symbolized by A), and Measures Orderid (an Integer, symbolized by #) and Overalldiscount (a Real, symbolized by 1.2) are primitive types. However, the Dimension Orderinfo is a Map data type, symbolized by [M].

When we click Edit Fields, we can see that while primitive types can be cast as alternate data types (such as Integer into Real), the complex data type Array cannot be changed to another type. However, the primitive components of the array may be cast as other primitive data types. Additionally, unlike other data types, uses complex datatypes only as Dimensions; they or their components cannot be re-defined as Measurements of the dataset.

MAPs in Visuals

When building a visual with complex data, you cannot use the complex type directly, as a whole. However, you can add the primitive components of the complex type to the shelves of the visual.

Changing Field Properties

It is very simple to change field properties for a component of a complex data type. You can change the aggregation function of a component, its type, the display options, and so on, just like a standalone primitive type field.

MAPs in Expression Editor

The expression editor supports the full use of MAPs, both in Dataset and Visual interfaces.