From 07d6d211f23f1d9d1d69fd54e8054bccd515bc8c Mon Sep 17 00:00:00 2001
From: Federico Caselli <cfederico87@gmail.com>
Date: Thu, 16 Apr 2020 23:16:32 +0200
Subject: Deprecate ``DISTINCT ON`` when not targeting PostgreSQL

Deprecate usage of ``DISTINCT ON`` in dialect other than PostgreSQL.
Previously this was silently ignored.
Deprecate old usage of string distinct in MySQL dialect

Fixes: #4002
Change-Id: I38fc64aef75e77748083c11d388ec831f161c9c9
---
 lib/sqlalchemy/sql/selectable.py | 3 +++
 1 file changed, 3 insertions(+)

(limited to 'lib/sqlalchemy/sql/selectable.py')

diff --git a/lib/sqlalchemy/sql/selectable.py b/lib/sqlalchemy/sql/selectable.py
index 89ee7e28f..c8df637ba 100644
--- a/lib/sqlalchemy/sql/selectable.py
+++ b/lib/sqlalchemy/sql/selectable.py
@@ -4138,6 +4138,9 @@ class Select(
          the PostgreSQL dialect will render a ``DISTINCT ON (<expressions>>)``
          construct.
 
+         .. deprecated:: 1.4 Using \*expr in other dialects is deprecated
+            and will raise :class:`_exc.CompileError` in a future version.
+
         """
         if expr:
             self._distinct = True
-- 
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