Add support for Exasol (#8343)

* Add support for Exasol

* add time grain functions for Exasol

* remove duplicate of

* override ExasolEngineSpec's fetch_data method

* remove duplicate https

* simplify super call

docs/index.rst

@@ -109,6 +109,7 @@ The following RDBMS are currently suppored:
 - `Apache Spark SQL <https://spark.apache.org/sql/>`_
 - `BigQuery <https://cloud.google.com/bigquery/>`_
 - `ClickHouse <https://clickhouse.yandex/>`_
+- `Exasol <https://www.exasol.com/>`_
 - `Google Sheets <https://www.google.com/sheets/about/>`_
 - `Greenplum <https://greenplum.org/>`_
 - `IBM Db2 <https://www.ibm.com/analytics/db2/>`_

docs/installation.rst

@@ -377,6 +377,8 @@ Here's a list of some of the recommended packages.
 +------------------+---------------------------------------+-------------------------------------------------+
 | ClickHouse       | ``pip install sqlalchemy-clickhouse`` |                                                 |
 +------------------+---------------------------------------+-------------------------------------------------+
+| Exasol           | ``pip install sqlalchemy-exasol``     | ``exa+pyodbc://``                               |
++------------------+---------------------------------------+-------------------------------------------------+
 | Google Sheets    | ``pip install gsheetsdb``             | ``gsheets://``                                  |
 +------------------+---------------------------------------+-------------------------------------------------+
 | IBM Db2          | ``pip install ibm_db_sa``             | ``db2+ibm_db://``                               |
@@ -659,6 +661,25 @@ it in the ``extra`` parameter::
     }
 
 
+Exasol
+---------
+
+The connection string for Exasol looks like this ::
+
+    exa+pyodbc://{user}:{password}@{host}
+
+*Note*: It's required to have Exasol ODBC drivers installed for the sqlalchemy dialect to work properly. Exasol ODBC Drivers available are here: https://www.exasol.com/portal/display/DOWNLOAD/Exasol+Download+Section
+
+Example config (odbcinst.ini can be left empty) ::
+
+    $ cat $/.../path/to/odbc.ini
+    [EXAODBC]
+    DRIVER = /.../path/to/driver/EXASOL_driver.so
+    EXAHOST = host:8563
+    EXASCHEMA = main
+
+See `SQLAlchemy for Exasol <https://github.com/blue-yonder/sqlalchemy_exasol>`_.
+
 CORS
 ----