Unnest object (flatten JSON)

Unnest, or flatten, JSON objects or arrays. By default, arrays are kept untouched.


The following JSON, jsoncol = {"firstname": "a", "lastname": "b", "details": { "uid": 237, "comment": " a comment"}, unnested to 1 level of depth yields:

  • jsoncol_firstname = a

  • jsoncol_lastname = b

  • jsoncol_details = {"uid": 237, “comment”: “a comment”}


Input column

Column containing a JSON object or array.

Maximum depth

Limit the depth at which the processor stops unnesting the JSON object or array.

Flatten arrays

By default, this processor does not flatten arrays when unnesting JSON. If the column contains a JSON array nested within a JSON object, the JSON array will be preserved as a single column. If the column contains a JSON array at the top level, the processor will do nothing.


Be aware that unnesting large arrays by selecting this option can lead to high memory and CPU consumption.

Convert null to empty cell

Convert a null value in a JSON property — flattened as a cell with the string “null” in it — to an empty cell.

Prefix output columns

Prefix output column names with the input column name.