Spawn¶

aggregating category: array no `||` new-mode: required resultSize: 1

Expands an ARRAY value into individual rows, fanning the chain out to one row per element.

Spawn(:array) consumes an ARRAY field and emits one row per element of the array. The first element becomes the primary result; the remaining elements become additional results, so downstream rules in the chain run once per element.

This is the new-mode replacement for the legacy multi-sized result fan-out: Spawn lets you defer fan-out from the producer (UsagiMap()[], Use()[N], …) to a later, explicit step that operates on an ARRAY collected up to that point. Available in new mode only.

Parameters¶

1 — array Mandatory — accepts: field: Field reference to an ARRAY-typed input. Each element of the array becomes one row in the downstream chain.

Input type¶

ARRAY

Output type¶

The element type of the input ARRAY. The rule reports ARRAY from aggregateType() purely to bypass the parse-time type check; elements are typed at runtime.

Requires¶

Exactly one parameter, a field reference to an ARRAY field.
The ARRAY must contain at least one element at runtime — empty arrays raise a runtime error.

Examples¶

Expand a collected ARRAY into one row per element

:codes => UsagiMap("file.csv")[] => :concept_array
Spawn(:concept_array)

Errors¶

`Spawn': input must be ARRAY-typed

The referenced field does not hold an ARRAY value at runtime.
`Spawn': empty array - no rows to produce

The ARRAY had zero elements when the rule fired.
Spawn: input:f' must be of ARRAY type`

The referenced field is not declared ARRAY.
`Spawn' is only available in new mode

New mode is not enabled in etl.conf.