.. _auto_dataset_unify_keys:

*UNIFY COLUMNS IN THE DATASET*
==============================

Finds the union of all column names present across every row in a dataset and ensures each row has a value for every discovered column. Missing values introduced by this alignment are filled according to the chosen null-replacement strategy (empty, average, min, or max). Use this worker to normalise ragged or schema-inconsistent datasets before downstream processing.

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

Classification: **process**.

Tagged: ``column_alignment``, ``null_fill``, ``process``, ``ragged_dataset``, ``schema_normalisation``, ``unify_keys``.

Inputs
------

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

   * - Label
     - ID
     - Type
     - Default
     - Required
     - Description
   * - Dataset
     - dataset
     - dataset
     - —
     - 
     - Input dataset whose rows may have inconsistent or missing columns; accepts any tabular dataset object — leave empty only if the dataset is piped directly from an upstream worker.
   * - Null Replacement Type
     - null_replacement_type
     - select
     - empty
     - 
     - Strategy used to fill values for columns that are absent in a given row: 'empty' (blank/null), 'average' (column mean), 'min' (column minimum), or 'max' (column maximum); defaults to 'empty'.

Outputs
-------

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

   * - Label
     - ID
     - Type
     - Description
   * - dataset_add_column_by_expression_output_1
     - dataset_add_column_by_expression_output_1
     - dataset
     - Unified dataset where every row contains the full set of columns discovered across all input rows, with missing values filled according to the selected null-replacement 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_unify_keys <https://www.d3view.com/api/workflow/example?id=dataset_unify_keys>`_

.. raw:: html

   <hr style="margin-top:2em">
   <p style="font-size:11px;color:#888">
   Auto-generated from <code>transformation</code> schema. Worker id: <code>dataset_unify_keys</code>. Schema hash: <code>db7ef77693f4</code>. Hand-curated docs in <code>workerexamples/</code> override this page when present.
   </p>