.. _auto_dataset_combine_keys_from_column:

*DATASET COMBINE KEYS FROM COLUMN*
==================================

Walks every row of the input dataset, extracts the nested dataset (or associative array / JSON string) stored in the target column, and merges all discovered keys into a single output row whose columns are those sub-dataset keys. Accepts nested datasets (list of rows), flat associative arrays, or JSON-encoded strings; on duplicate keys the collision strategy controls which value survives.

When to use
-----------

Classification: **process**.

Tagged: ``associative-array``, ``combine``, ``flatten``, ``json-decode``, ``key-collision``, ``nested-dataset``, ``pivot``, ``single-row``.

Inputs
------

.. list-table::
   :header-rows: 1
   :widths: 20 20 20 20 20 20

   * - Label
     - ID
     - Type
     - Default
     - Required
     - Description
   * - Dataset
     - dataset_1
     - dataset
     - —
     - 
     - Input dataset whose rows each carry a nested dataset, flat associative array, or JSON-encoded object in the column specified by `column_name`.
   * - Column Name
     - column_name
     - scalar
     - —
     - 
     - Name of the column that holds the per-row associative array or nested dataset to be unpacked; must be an existing column in `dataset_1`.
   * - On Key Collision
     - on_collision
     - scalar
     - last_wins
     - 
     - Strategy when two sub-rows share the same key: `last_wins` (default) keeps the last encountered value, `first_wins` keeps the first, and `prefix_with_row_index` disambiguates by prepending the source row index.

Outputs
-------

.. list-table::
   :header-rows: 1
   :widths: 20 20 20 20

   * - Label
     - ID
     - Type
     - Description
   * - dataset_combine_keys_from_column_output_1
     - dataset_combine_keys_from_column_output_1
     - dataset
     - Single-row dataset whose column names are the union of all keys found across every sub-row extracted from the target column, with values resolved according to the collision strategy.

Disciplines
-----------

- data.dataset.transform

Runnable example
----------------

A runnable example is registered for this worker. Open the example workflow on the d3VIEW canvas: `/api/workflow/example?id=dataset_combine_keys_from_column <https://www.d3view.com/api/workflow/example?id=dataset_combine_keys_from_column>`_

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   <hr style="margin-top:2em">
   <p style="font-size:11px;color:#888">
   Auto-generated from <code>transformation</code> schema. Worker id: <code>dataset_combine_keys_from_column</code>. Schema hash: <code>4c7860f93e3a</code>. Hand-curated docs in <code>workerexamples/</code> override this page when present.
   </p>