Adding a doc page for Druid

docs/druid.rst

@@ -0,0 +1,48 @@
+Druid
+=====
+
+Caravel works well with Druid, though currently not all
+advanced features out of Druid are covered. This page clarifies what is
+covered and what isn't and explains how to use some of the features.
+
+.. note ::
+    Currently Airbnb runs against Druid ``0.8.x`` and previous /
+    following versions are not tested against.
+
+Supported
+'''''''''
+
+Aggregations
+------------
+
+Common aggregations, or Druid metrics can be defined and used in Caravel.
+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 they their ``json``
+element correspond to Druid aggregation definition. You can create your own
+aggregations manually from the ``List Druid Metric`` tab following Druid
+documentation.
+
+.. image:: _static/img/druid_agg.png
+   :scale: 50 %
+
+Post-Aggregations
+-----------------
+
+Druid supports post aggregation and this works in Caravel. All you have to
+do is creating 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.
+
+
+Not yet supported
+'''''''''''''''''
+
+- Regex filters
+- Lookups / joins

docs/index.rst

@@ -34,6 +34,7 @@ Contents
     tutorial
     videos
     gallery
+    druid
     faq