Merge "Deprecate ``DISTINCT ON`` when not targeting PostgreSQL"

3 files changed, 32 insertions, 0 deletions

diff --git a/test/dialect/mysql/test_deprecations.py b/test/dialect/mysql/test_deprecations.py
index 544284a21..b2bd99d82 100644
--- a/test/dialect/mysql/test_deprecations.py
+++ b/test/dialect/mysql/test_deprecations.py
@@ -1,9 +1,29 @@
+from sqlalchemy import select
+from sqlalchemy import table
+from sqlalchemy.dialects.mysql import base as mysql
 from sqlalchemy.dialects.mysql import ENUM
 from sqlalchemy.dialects.mysql import SET
+from sqlalchemy.testing import AssertsCompiledSQL
+from sqlalchemy.testing import expect_deprecated
 from sqlalchemy.testing import expect_deprecated_20
 from sqlalchemy.testing import fixtures
 
 
+class CompileTest(AssertsCompiledSQL, fixtures.TestBase):
+
+    __dialect__ = mysql.dialect()
+
+    def test_distinct_string(self):
+        s = select(["*"]).select_from(table("foo"))
+        s._distinct = "foo"
+
+        with expect_deprecated(
+            "Sending string values for 'distinct' is deprecated in the MySQL "
+            "dialect and will be removed in a future release"
+        ):
+            self.assert_compile(s, "SELECT FOO * FROM foo")
+
+
 class DeprecateQuoting(fixtures.TestBase):
     def test_enum_warning(self):
         ENUM("a", "b")
diff --git a/test/requirements.py b/test/requirements.py
index aac376dba..cf9168f5a 100644
--- a/test/requirements.py
+++ b/test/requirements.py
@@ -1611,3 +1611,8 @@ class DefaultRequirements(SuiteRequirements):
     @property
     def computed_columns_reflect_persisted(self):
         return self.computed_columns + skip_if("oracle")
+
+    @property
+    def supports_distinct_on(self):
+        """If a backend supports the DISTINCT ON in a select"""
+        return only_if(["postgresql"])
diff --git a/test/sql/test_compiler.py b/test/sql/test_compiler.py
index e44deed90..440eaa05a 100644
--- a/test/sql/test_compiler.py
+++ b/test/sql/test_compiler.py
@@ -1462,6 +1462,13 @@ class SelectTest(fixtures.TestBase, AssertsCompiledSQL):
             "SELECT count(DISTINCT mytable.myid) AS count_1 FROM mytable",
         )
 
+    def test_distinct_on(self):
+        with testing.expect_deprecated(
+            "DISTINCT ON is currently supported only by the PostgreSQL "
+            "dialect"
+        ):
+            select(["*"]).distinct(table1.c.myid).compile()
+
     def test_where_empty(self):
         self.assert_compile(
             select([table1.c.myid]).where(