Druid
=====

Superset has a native connector to Druid and a majority of Druid's
features are accessible through Superset.

.. note ::
    Druid now supports SQL and can be accessed through Superset's
    SQLAlchemy connector. The long-term vision is to deprecate
    the Druid native REST connector and query Druid exclusively through
    the SQL interface.

Aggregations
------------

Common aggregations or Druid metrics can be defined and used in Superset.
The first and simpler use case is to use the checkbox matrix expose in your
datasource's edit view (``Sources -> Druid Datasources ->
[your datasource] -> Edit -> [tab] List Druid Column``).
Clicking the ``GroupBy`` and ``Filterable`` checkboxes will make the column
appear in the related dropdowns while in explore view. Checking
``Count Distinct``, ``Min``, ``Max`` or ``Sum`` will result in creating
new metrics that will appear in the ``List Druid Metric`` tab upon saving the
datasource. By editing these metrics, you'll notice that their ``json``
element corresponds to Druid aggregation definition. You can create your own
aggregations manually from the ``List Druid Metric`` tab following Druid
documentation.

.. image:: images/druid_agg.png
   :scale: 50 %

Post-Aggregations
-----------------

Druid supports post aggregation and this works in Superset. All you have to
do is create a metric, much like you would create an aggregation manually,
but specify ``postagg`` as a ``Metric Type``. You then have to provide a valid
json post-aggregation definition (as specified in the Druid docs) in the
Json field.


Unsupported Features
--------------------

.. note ::
    Unclear at this point, this section of the documentation could use
    some input.