DSQL element path

Looping context

To understand paths in DSQL maps, it is important to understand the concept of looping context. The looping context describes how to handle elements that can occur multiple times in a structure. In the map below, the output structure has a loop element named items. This element needs a looping context that will associate it with one of the loops in the input structure. In this case, the output should contain one items element for each items occurrence in each departments loop in the input structure. This is defined with the following expression:

FROM departments
UNNEST items

The output items element's looping context is the input items element.

Absolute path

Relative path

An element cannot be referenced with a relative path if the path can be ambiguous. In the example above, the input structure contains multiple elements named name under different loops. If the looping context is the input items element, only the name element under items can be referenced with the relative path name. The other name elements must be referenced with their absolute path, plusstore.departments.name for example.

If the looping context changes, some relative paths may be automatically changed to absolute paths if needed. If the looping context in the example above is originally the plusstore.departments loop, you can refer to plusstore.departments.name in the output department_name element with the relative path name. If you then change the looping context to the plusstore.departments.items loop, the relative path name can only refer to plusstore.departments.items.name and the expression in the output department_name element is updated to the absolute path plusstore.departments.name.

For an example of looping contexts and relative paths, see Mapping nested loops in a DSQL map.