Use full column->type processing for ON CONFLICT SET clause

Fixed bug in new "ON CONFLICT DO UPDATE" feature where the "set"
values for the UPDATE clause would not be subject to type-level
processing, as normally takes effect to handle both user-defined
type level conversions as well as dialect-required conversions, such
as those required for JSON datatypes.   Additionally, clarified that
the keys in the set_ dictionary should match the "key" of the column,
if distinct from the column name.  A warning is emitted
for remaining column names that don't match column keys; for
compatibility reasons, these are emitted as they were previously.

Fixes: #3888
Change-Id: I67a04c67aa5f65e6d29f27bf3ef2f8257088d073

1 files changed, 3 insertions, 1 deletions

diff --git a/lib/sqlalchemy/dialects/postgresql/dml.py b/lib/sqlalchemy/dialects/postgresql/dml.py
index df53fa8a2..bfdfbfa36 100644
--- a/lib/sqlalchemy/dialects/postgresql/dml.py
+++ b/lib/sqlalchemy/dialects/postgresql/dml.py
@@ -70,6 +70,8 @@ class Insert(StandardInsert):
         Required argument. A dictionary or other mapping object
         with column names as keys and expressions or literals as values,
         specifying the ``SET`` actions to take.
+        If the target :class:`.Column` specifies a ".key" attribute distinct
+        from the column name, that key should be used.
 
         .. warning:: This dictionary does **not** take into account
            Python-specified default UPDATE values or generation functions,
@@ -205,7 +207,7 @@ class OnConflictDoUpdate(OnConflictClause):
         if (not isinstance(set_, dict) or not set_):
             raise ValueError("set parameter must be a non-empty dictionary")
         self.update_values_to_set = [
-            (key, _literal_as_binds(value))
+            (key, value)
             for key, value in set_.items()
         ]
         self.update_whereclause = where