Map state input and output fields in Step Functions - AWS Step Functions

Map state input and output fields in Step Functions

Managing state and transforming data

Learn about Passing data between states with variables and Transforming data with JSONata.

Map states iterate over a collection of items in a dataset. Examples of data sets include:

  • JSON arrays and objects from previous states.

  • Individual data files stored in Amazon S3 in formats such as: JSON, JSONL, CSV, Parquet files.

  • References to multiple objects, such as: Athena manifests and Amazon S3 inventory files

A map repeats a set of steps for each item in the dataset. You can configure the input that the Map state receives and the output the map generates using a variety of configuration options. Step Functions applies each option in your Distributed Map state in the order shown in the following list. Depending on your use case, you may not need to apply all of fields.

  1. ItemReader (Map) - used to read your data items

  2. ItemsPath (Map, JSONPath only) or Items (JSONata) - optional; used to specify items in your dataset

  3. ItemSelector (Map) - optional; used to select and modify items in the data set

  4. ItemBatcher (Map) - used to process groups of items when processing large sets of items

  5. ResultWriter (Map) - provides options for output results from child workflows