refactor impl

Author: geooo109

sqlglot/optimizer/annotate_types.py

@@ -213,6 +213,11 @@ def __init__(
         # When set to False, this enables partial annotation by skipping already-annotated nodes
         self._overwrite_types = overwrite_types
 
+    def clean(self) -> None:
+        self._visited.clear()
+        self._null_expressions.clear()
+        self._setop_column_types.clear()
+
     def _set_type(
         self, expression: exp.Expression, target_type: t.Optional[exp.DataType | exp.DataType.Type]
     ) -> None: