Refs #34320 -- Stopped recreating check constraints when renaming fields.

felixxm · web-flow · commit 9953c804a937 · 2023-03-02T06:05:40.000+01:00
This also fixes test_rename_field_with_check_to_truncated_name() on
MariaDB 10.5.2+ as ALTER TABLE ... RENAME COLUMN statement doesn't
rename inline constraints.
diff --git a/django/db/backends/base/schema.py b/django/db/backends/base/schema.py
@@ -838,6 +838,17 @@ def alter_field(self, model, old_field, new_field, strict=False):
             strict,
         )
 
+    def _field_db_check(self, field, field_db_params):
+        # Always check constraints with the same mocked column name to avoid
+        # recreating constrains when the column is renamed.
+        check_constraints = self.connection.data_type_check_constraints
+        data = field.db_type_parameters(self.connection)
+        data["column"] = "__column_name__"
+        try:
+            return check_constraints[field.get_internal_type()] % data
+        except KeyError:
+            return None
+
     def _alter_field(
         self,
         model,
@@ -956,7 +967,9 @@ def _alter_field(
                 # is to look at its name (refs #28053).
                 self.execute(self._delete_index_sql(model, index_name))
         # Change check constraints?
-        if old_db_params["check"] != new_db_params["check"] and old_db_params["check"]:
+        old_db_check = self._field_db_check(old_field, old_db_params)
+        new_db_check = self._field_db_check(new_field, new_db_params)
+        if old_db_check != new_db_check and old_db_check:
             meta_constraint_names = {
                 constraint.name for constraint in model._meta.constraints
             }
@@ -1162,7 +1175,7 @@ def _alter_field(
                         self._create_fk_sql(rel.related_model, rel.field, "_fk")
                     )
         # Does it have check constraints we need to add?
-        if old_db_params["check"] != new_db_params["check"] and new_db_params["check"]:
+        if old_db_check != new_db_check and new_db_check:
             constraint_name = self._create_index_name(
                 model._meta.db_table, [new_field.column], suffix="_check"
             )
diff --git a/django/db/backends/mysql/schema.py b/django/db/backends/mysql/schema.py
@@ -230,6 +230,19 @@ def _alter_column_type_sql(
             model, old_field, new_field, new_type, old_collation, new_collation
         )
 
+    def _field_db_check(self, field, field_db_params):
+        if self.connection.mysql_is_mariadb and self.connection.mysql_version >= (
+            10,
+            5,
+            2,
+        ):
+            return super()._field_db_check(field, field_db_params)
+        # On MySQL and MariaDB < 10.5.2 (no support for
+        # "ALTER TABLE ... RENAME COLUMN" statements), check constraints with
+        # the column name as it requires explicit recreation when the column is
+        # renamed.
+        return field_db_params["check"]
+
     def _rename_field_sql(self, table, old_field, new_field, new_type):
         new_type = self._set_field_new_type_null_status(old_field, new_type)
         return super()._rename_field_sql(table, old_field, new_field, new_type)
