Add support for Apache Drill (#6610)

* Add support for Apache Drill

* Updated Docs

* Removed Extraneous Functions

* Removed Extraneous Functions

* Final Mods

* Fixed Unit Test Error

* Fixed Epoch Conversion Functions

docs/installation.rst

@@ -392,6 +392,12 @@ Here's a list of some of the recommended packages.
 |  Pinot        | ``pip install pinotdb``             | ``pinot+http://controller:5436/``               |
 |               |                                     | ``query?server=http://controller:5983/``        |
 +---------------+-------------------------------------+-------------------------------------------------+
+|  Apache Drill |                                     | For the REST API:``                             |
+|               |                                     | ``drill+sadrill://``                            |
+|               |                                     | For JDBC                                        |
+|               |                                     | ``drill+jdbc://``                               |
++---------------+-------------------------------------+-------------------------------------------------+
+
 
 Note that many other databases are supported, the main criteria being the
 existence of a functional SqlAlchemy dialect and Python driver. Googling
@@ -449,6 +455,31 @@ Required environment variables: ::
 
 See `Teradata SQLAlchemy <https://github.com/Teradata/sqlalchemy-teradata>`_.
 
+Apache Drill
+---------
+At the time of writing, the SQLAlchemy Dialect is not available on pypi and must be downloaded here:
+`SQLAlchemy Drill <https://github.com/JohnOmernik/sqlalchemy-drill>`_
+
+Alternatively, you can install it completely from the command line as follows: ::
+
+    git clone https://github.com/JohnOmernik/sqlalchemy-drill
+    cd sqlalchemy-drill
+    python3 setup.py install
+
+Once that is done, you can connect to Drill in two ways, either via the REST interface or by JDBC.  If you are connecting via JDBC, you must have the
+Drill JDBC Driver installed.
+
+The basic connection string for Drill looks like this ::
+
+    drill+sadrill://{username}:{password}@{host}:{port}/{storage_plugin}?use_ssl=True
+
+If you are using JDBC to connect to Drill, the connection string looks like this: ::
+
+    drill+jdbc://{username}:{password}@{host}:{port}/{storage_plugin}
+
+For a complete tutorial about how to use Apache Drill with Superset, see this tutorial:
+`Visualize Anything with Superset and Drill <http://thedataist.com/visualize-anything-with-superset-and-drill/>`_
+
 Caching
 -------
 

superset/db_engine_specs.py

@@ -724,6 +724,50 @@ class SqliteEngineSpec(BaseEngineSpec):
         return sorted(inspector.get_table_names())
 
 
+class DrillEngineSpec(BaseEngineSpec):
+    """Engine spec for Apache Drill"""
+    engine = 'drill'
+
+    time_grain_functions = {
+        None: '{col}',
+        'PT1S': "nearestDate({col}, 'SECOND')",
+        'PT1M': "nearestDate({col}, 'MINUTE')",
+        'PT15M': "nearestDate({col}, 'QUARTER_HOUR')",
+        'PT0.5H': "nearestDate({col}, 'HALF_HOUR')",
+        'PT1H': "nearestDate({col}, 'HOUR')",
+        'P1D': 'TO_DATE({col})',
+        'P1W': "nearestDate({col}, 'WEEK_SUNDAY')",
+        'P1M': "nearestDate({col}, 'MONTH')",
+        'P0.25Y': "nearestDate({col}, 'QUARTER')",
+        'P1Y': "nearestDate({col}, 'YEAR')",
+    }
+
+    # Returns a function to convert a Unix timestamp in milliseconds to a date
+    @classmethod
+    def epoch_to_dttm(cls):
+        return cls.epoch_ms_to_dttm().replace('{col}', '({col}*1000)')
+
+    @classmethod
+    def epoch_ms_to_dttm(cls):
+        return 'TO_DATE({col})'
+
+    @classmethod
+    def convert_dttm(cls, target_type, dttm):
+        tt = target_type.upper()
+        if tt == 'DATE':
+            return "CAST('{}' AS DATE)".format(dttm.isoformat()[:10])
+        elif tt == 'TIMESTAMP':
+            return "CAST('{}' AS TIMESTAMP)".format(
+                dttm.strftime('%Y-%m-%d %H:%M:%S'))
+        return "'{}'".format(dttm.strftime('%Y-%m-%d %H:%M:%S'))
+
+    @classmethod
+    def adjust_database_uri(cls, uri, selected_schema):
+        if selected_schema:
+            uri.database = parse.quote(selected_schema, safe='')
+        return uri
+
+
 class MySQLEngineSpec(BaseEngineSpec):
     engine = 'mysql'
     max_column_name_length = 64