From: Mike Bayer <mike_mp@zzzcomputing.com>
Date: Fri, 6 Dec 2019 16:38:55 +0000 (-0500)
Subject: Use label reference coercion for select() distinct keyword argument
X-Git-Tag: rel_1_4_0b1~603
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=926952c4afe0b2e16c4a74f05958bded7b932760;p=thirdparty%2Fsqlalchemy%2Fsqlalchemy.git

Use label reference coercion for select() distinct keyword argument

Fixed bug where "distinct" keyword passed to :func:`.select` would not
treat a string value as a "label reference" in the same way that the
:meth:`.select.distinct` does; it would instead raise unconditionally. This
keyword argument and the others passed to :func:`.select` will ultimately
be deprecated for SQLAlchemy 2.0.

Fixes: #5028
Change-Id: Id36cfe477ed836c3248824ce1b81d0016dbe99f4
---

diff --git a/doc/build/changelog/unreleased_13/5028.rst b/doc/build/changelog/unreleased_13/5028.rst
new file mode 100644
index 0000000000..be2a354c25
--- /dev/null
+++ b/doc/build/changelog/unreleased_13/5028.rst
@@ -0,0 +1,10 @@
+.. change::
+    :tags: bug, sql
+    :tickets: 5028
+
+    Fixed bug where "distinct" keyword passed to :func:`.select` would not
+    treat a string value as a "label reference" in the same way that the
+    :meth:`.select.distinct` does; it would instead raise unconditionally. This
+    keyword argument and the others passed to :func:`.select` will ultimately
+    be deprecated for SQLAlchemy 2.0.
+
diff --git a/lib/sqlalchemy/sql/selectable.py b/lib/sqlalchemy/sql/selectable.py
index 4b3844eec1..0eadab6107 100644
--- a/lib/sqlalchemy/sql/selectable.py
+++ b/lib/sqlalchemy/sql/selectable.py
@@ -3388,7 +3388,7 @@ class Select(
             if not isinstance(distinct, bool):
                 self._distinct_on = tuple(
                     [
-                        coercions.expect(roles.WhereHavingRole, e)
+                        coercions.expect(roles.ByOfRole, e)
                         for e in util.to_list(distinct)
                     ]
                 )
diff --git a/test/sql/test_text.py b/test/sql/test_text.py
index 3386d0aae9..ae4be65ad6 100644
--- a/test/sql/test_text.py
+++ b/test/sql/test_text.py
@@ -747,6 +747,15 @@ class OrderByLabelResolutionTest(fixtures.TestBase, AssertsCompiledSQL):
             dialect="postgresql",
         )
 
+    def test_distinct_label_keyword(self):
+
+        stmt = select([table1.c.myid.label("foo")], distinct="foo")
+        self.assert_compile(
+            stmt,
+            "SELECT DISTINCT ON (foo) mytable.myid AS foo FROM mytable",
+            dialect="postgresql",
+        )
+
     def test_unresolvable_distinct_label(self):
         from sqlalchemy.dialects import postgresql