Emit DROP CHECK for MySQL, DROP CONSTRAINT for MariaDB

Added support for MySQL "DROP CHECK", which is added as of MySQL 8.0.16,
separate from MariaDB's "DROP CONSTRAINT" for CHECK constraints.  The MySQL
Alembic implementation now checks for "MariaDB" in server_version_info to
decide which one to use.

Change-Id: I22d1eb084570769ec11b654bc01af3a0938d9a7c
Fixes: #554

diff --git a/alembic/ddl/mysql.py b/alembic/ddl/mysql.py
index f886f104c5dbec6181c09c85c957f354b102cab5..504eb4c68322a36557e579546de5c55bce050c31 100644 (file)
--- a/alembic/ddl/mysql.py
+++ b/alembic/ddl/mysql.py
@@ -16,6 +16,7 @@ from .impl import DefaultImpl
 from .. import util
 from ..autogenerate import compare
 from ..util.compat import string_types
+from ..util.sqla_compat import _is_mariadb
 from ..util.sqla_compat import _is_type_bound
 from ..util.sqla_compat import sqla_100
 
@@ -126,9 +127,11 @@ class MySQLImpl(DefaultImpl):
         ):
             return False
         elif inspector_column.type._type_affinity is sqltypes.Integer:
-            rendered_inspector_default = re.sub(
-                r"^'|'$", "", rendered_inspector_default
-            ) if rendered_inspector_default is not None else None
+            rendered_inspector_default = (
+                re.sub(r"^'|'$", "", rendered_inspector_default)
+                if rendered_inspector_default is not None
+                else None
+            )
             return rendered_inspector_default != rendered_metadata_default
         elif rendered_inspector_default and rendered_metadata_default:
             # adjust for "function()" vs. "FUNCTION"
@@ -403,10 +406,16 @@ def _mysql_drop_constraint(element, compiler, **kw):
         # note that SQLAlchemy as of 1.2 does not yet support
         # DROP CONSTRAINT for MySQL/MariaDB, so we implement fully
         # here.
-        return "ALTER TABLE %s DROP CONSTRAINT %s" % (
-            compiler.preparer.format_table(constraint.table),
-            compiler.preparer.format_constraint(constraint),
-        )
+        if _is_mariadb(compiler.dialect):
+            return "ALTER TABLE %s DROP CONSTRAINT %s" % (
+                compiler.preparer.format_table(constraint.table),
+                compiler.preparer.format_constraint(constraint),
+            )
+        else:
+            return "ALTER TABLE %s DROP CHECK %s" % (
+                compiler.preparer.format_table(constraint.table),
+                compiler.preparer.format_constraint(constraint),
+            )
     else:
         raise NotImplementedError(
             "No generic 'DROP CONSTRAINT' in MySQL - "

diff --git a/alembic/testing/fixtures.py b/alembic/testing/fixtures.py
index e0b8fdfbb6644c562a4afbad492b855b4de5cd67..96bb58396e3d3fda193a8c8a9782dc772366870f 100644 (file)
--- a/alembic/testing/fixtures.py
+++ b/alembic/testing/fixtures.py
@@ -152,7 +152,12 @@ def op_fixture(
         opts["as_sql"] = as_sql
     if literal_binds:
         opts["literal_binds"] = literal_binds
-    ctx_dialect = _get_dialect(dialect)
+    if dialect == "mariadb":
+        ctx_dialect = _get_dialect("mysql")
+        ctx_dialect.server_version_info = (10, 0, 0, "MariaDB")
+
+    else:
+        ctx_dialect = _get_dialect(dialect)
     if native_boolean is not None:
         ctx_dialect.supports_native_boolean = native_boolean
         # this is new as of SQLAlchemy 1.2.7 and is used by SQL Server,

diff --git a/alembic/util/sqla_compat.py b/alembic/util/sqla_compat.py
index 82250d00f970195ece8d3f3f03f3e284188f853a..52d4e018161049b3e1a47343aa9f41f9db612a89 100644 (file)
--- a/alembic/util/sqla_compat.py
+++ b/alembic/util/sqla_compat.py
@@ -233,7 +233,10 @@ def _comment_attribute(obj):
 
 
 def _is_mariadb(mysql_dialect):
-    return "MariaDB" in mysql_dialect.server_version_info
+    return (
+        mysql_dialect.server_version_info
+        and "MariaDB" in mysql_dialect.server_version_info
+    )
 
 
 def _mariadb_normalized_version_info(mysql_dialect):

diff --git a/docs/build/unreleased/554.rst b/docs/build/unreleased/554.rst
new file mode 100644 (file)
index 0000000..02bbd68
--- /dev/null
+++ b/docs/build/unreleased/554.rst
@@ -0,0 +1,10 @@
+.. change::
+   :tags: bug, mysql
+   :tickets: 554
+
+   Added support for MySQL "DROP CHECK", which is added as of MySQL 8.0.16,
+   separate from MariaDB's "DROP CONSTRAINT" for CHECK constraints.  The MySQL
+   Alembic implementation now checks for "MariaDB" in server_version_info to
+   decide which one to use.
+
+

diff --git a/tests/test_mysql.py b/tests/test_mysql.py
index 6e841e4bda01522c348076cfed3add48578f367f..6e0db82e5f3d15b767da6cd4a1267e3c388ff8f3 100644 (file)
--- a/tests/test_mysql.py
+++ b/tests/test_mysql.py
@@ -348,16 +348,26 @@ class MySQLOpTest(TestBase):
         op.drop_constraint("MyUnique", "MyTable", "unique")
         context.assert_("ALTER TABLE `MyTable` DROP INDEX `MyUnique`")
 
-    def test_drop_check(self):
-        context = op_fixture("mysql")
+    def test_drop_check_mariadb(self):
+        context = op_fixture("mariadb")
         op.drop_constraint("f1", "t1", "check")
         context.assert_("ALTER TABLE t1 DROP CONSTRAINT f1")
 
-    def test_drop_check_quoted(self):
-        context = op_fixture("mysql")
+    def test_drop_check_quoted_mariadb(self):
+        context = op_fixture("mariadb")
         op.drop_constraint("MyCheck", "MyTable", "check")
         context.assert_("ALTER TABLE `MyTable` DROP CONSTRAINT `MyCheck`")
 
+    def test_drop_check_mysql(self):
+        context = op_fixture("mysql")
+        op.drop_constraint("f1", "t1", "check")
+        context.assert_("ALTER TABLE t1 DROP CHECK f1")
+
+    def test_drop_check_quoted_mysql(self):
+        context = op_fixture("mysql")
+        op.drop_constraint("MyCheck", "MyTable", "check")
+        context.assert_("ALTER TABLE `MyTable` DROP CHECK `MyCheck`")
+
     def test_drop_unknown(self):
         op_fixture("mysql")
         assert_raises_message(