[docs] CTAS on PostgreSQL needs commit to apply (#8367)

* [docs] New, document need for PG to use autocommit for CTAS

docs/installation.rst

@@ -579,6 +579,9 @@ object gets unpacked into the
 while the ``metadata_params`` get unpacked into the
 `sqlalchemy.MetaData <https://docs.sqlalchemy.org/en/rel_1_2/core/metadata.html#sqlalchemy.schema.MetaData>`_ call. Refer to the SQLAlchemy docs for more information.
 
+.. note:: If your using CTAS on SQLLab and PostgreSQL
+    take a look at :ref:`ref_ctas_engine_config` for specific ``engine_params``.
+
 
 Schemas (Postgres & Redshift)
 -----------------------------

docs/sqllab.rst

@@ -122,3 +122,22 @@ database configuration:
 
 Here, "version" should be the version of your Presto cluster. Support for this
 functionality was introduced in Presto 0.319.
+
+.. _ref_ctas_engine_config:
+
+Create Table As (CTAS)
+''''''''''''''''''''''
+
+You can use ``CREATE TABLE AS SELECT ...`` statements on SQLLab. This feature can be toggled on
+and off at the database configuration level.
+
+Note that since ``CREATE TABLE..`` belongs to a SQL DDL category. Specifically on PostgreSQL, DDL is transactional,
+this means that to properly use this feature you have to set ``autocommit`` to true on your engine parameters:
+
+.. code-block:: json
+
+    {
+        ...
+        "engine_params": {"isolation_level":"AUTOCOMMIT"},
+        ...
+    }