Render VALUES within composed MySQL on duplicate key expressions

Fixed issue in MySQL :meth:`.mysql.Insert.on_duplicate_key_update` construct
where using a SQL function or other composed expression for a column argument
would not properly render the ``VALUES`` keyword surrounding the column
itself.

Fixes: #5173
Change-Id: I16d39c2fdb8bbb7f3d1b2ffdd20e1bf69359ab75

2 files changed, 42 insertions, 0 deletions

diff --git a/test/dialect/mysql/test_compiler.py b/test/dialect/mysql/test_compiler.py
index d59c0549f..e74c37d63 100644
--- a/test/dialect/mysql/test_compiler.py
+++ b/test/dialect/mysql/test_compiler.py
@@ -928,3 +928,28 @@ class InsertOnDuplicateTest(fixtures.TestBase, AssertsCompiledSQL):
             "ON DUPLICATE KEY UPDATE bar = %s"
         )
         self.assert_compile(stmt, expected_sql)
+
+    def test_update_sql_expr(self):
+        stmt = insert(self.table).values(
+            [{"id": 1, "bar": "ab"}, {"id": 2, "bar": "b"}]
+        )
+        stmt = stmt.on_duplicate_key_update(
+            bar=func.coalesce(stmt.inserted.bar),
+            baz=stmt.inserted.baz + "some literal",
+        )
+        expected_sql = (
+            "INSERT INTO foos (id, bar) VALUES (%s, %s), (%s, %s) ON "
+            "DUPLICATE KEY UPDATE bar = coalesce(VALUES(bar)), "
+            "baz = (concat(VALUES(baz), %s))"
+        )
+        self.assert_compile(
+            stmt,
+            expected_sql,
+            checkparams={
+                "id_m0": 1,
+                "bar_m0": "ab",
+                "id_m1": 2,
+                "bar_m1": "b",
+                "baz_1": "some literal",
+            },
+        )
diff --git a/test/dialect/mysql/test_on_duplicate.py b/test/dialect/mysql/test_on_duplicate.py
index 077e5ba98..439648153 100644
--- a/test/dialect/mysql/test_on_duplicate.py
+++ b/test/dialect/mysql/test_on_duplicate.py
@@ -77,6 +77,23 @@ class OnDuplicateTest(fixtures.TablesTest):
                 [(1, "b", "bz", None)],
             )
 
+    def test_on_duplicate_key_update_expression(self):
+        foos = self.tables.foos
+        with testing.db.connect() as conn:
+            conn.execute(insert(foos, dict(id=1, bar="b", baz="bz")))
+            stmt = insert(foos).values(
+                [dict(id=1, bar="ab"), dict(id=2, bar="b")]
+            )
+            stmt = stmt.on_duplicate_key_update(
+                bar=func.concat(stmt.inserted.bar, "_foo")
+            )
+            result = conn.execute(stmt)
+            eq_(result.inserted_primary_key, [2])
+            eq_(
+                conn.execute(foos.select().where(foos.c.id == 1)).fetchall(),
+                [(1, "ab_foo", "bz", False)],
+            )
+
     def test_on_duplicate_key_update_preserve_order(self):
         foos = self.tables.foos
         with testing.db.connect() as conn: