Batch Transform

Applies a function to each item of an array and hands the array on as one message. The items are processed in parallel.

Type: batch-transform · Category: Transform · Ports: one input · one output

When to use it

• Converting units, renaming fields or enriching every row of a result set
• Any per-item work where the items do not depend on each other

Reach for something else when

If each item must travel through the rest of the graph on its own — one HTTP call per row, say — use Array Iterator instead.

Settings

Setting	Key	Default	Purpose
Transform type	transformType	map	How items are combined back.
Code	code	—	The per-item function.
Payload	payloadType / payloadValue	msg	Where the collection comes from.

Example — converting a batch of readings

def transform(item, message):
    """
    :param item: the current item from the incoming array
    :param message: the parent message context
    :return: the transformed item
    """
    return {**item, "celsius": round((item["fahrenheit"] - 32) * 5 / 9, 2)}

In

{ "payload": [ { "sensor": "T1", "fahrenheit": 160.2 },
               { "sensor": "T2", "fahrenheit": 158.8 } ] }

Out

{ "payload": [ { "sensor": "T1", "fahrenheit": 160.2, "celsius": 71.22 },
               { "sensor": "T2", "fahrenheit": 158.8, "celsius": 70.44 } ] }

Gotchas

• Ordering across items is not guaranteed, because they run in parallel. Never accumulate into shared state here — compute per item and combine afterwards.

See also

• Array Iterator