document missing ColumnCollection methods

add additional notes regarding the methods that are on this
object.

Fixes: #6629
Change-Id: I68446cb16cbfcef9af9c2998687b3b536607cf0d

1 files changed, 11 insertions, 0 deletions

diff --git a/lib/sqlalchemy/dialects/postgresql/dml.py b/lib/sqlalchemy/dialects/postgresql/dml.py
index b6f5cdf7e..c98bc9f76 100644
--- a/lib/sqlalchemy/dialects/postgresql/dml.py
+++ b/lib/sqlalchemy/dialects/postgresql/dml.py
@@ -44,6 +44,17 @@ class Insert(StandardInsert):
         be inserted, known as ``excluded``.  This attribute provides
         all columns in this row to be referenceable.
 
+        .. tip::  The :attr:`_postgresql.Insert.excluded` attribute is an
+            instance of :class:`_expression.ColumnCollection`, which provides
+            an interface the same as that of the :attr:`_schema.Table.c`
+            collection described at :ref:`metadata_tables_and_columns`.
+            With this collection, ordinary names are accessible like attributes
+            (e.g. ``stmt.excluded.some_column``), but special names and
+            dictionary method names should be accessed using indexed access,
+            such as ``stmt.excluded["column name"]`` or
+            ``stmt.excluded["values"]``.   See the docstring for
+            :class:`_expression.ColumnCollection` for further examples.
+
         .. seealso::
 
             :ref:`postgresql_insert_on_conflict` - example of how