3 files changed, 31 insertions, 42 deletions

diff --git a/lib/sqlalchemy/sql/compiler.py b/lib/sqlalchemy/sql/compiler.py
index 04ae2532b..9c1f50ce1 100644
--- a/lib/sqlalchemy/sql/compiler.py
+++ b/lib/sqlalchemy/sql/compiler.py
@@ -3542,6 +3542,12 @@ class DDLCompiler(Compiled):
         else:
             return None
 
+    def visit_table_or_column_check_constraint(self, constraint, **kw):
+        if constraint.is_column_level:
+            return self.visit_column_check_constraint(constraint)
+        else:
+            return self.visit_check_constraint(constraint)
+
     def visit_check_constraint(self, constraint):
         text = ""
         if constraint.name is not None:
diff --git a/lib/sqlalchemy/sql/schema.py b/lib/sqlalchemy/sql/schema.py
index 7cece42d0..e6d3a6b05 100644
--- a/lib/sqlalchemy/sql/schema.py
+++ b/lib/sqlalchemy/sql/schema.py
@@ -2238,14 +2238,6 @@ class ColumnDefault(DefaultGenerator):
                 "positional arguments"
             )
 
-    def _visit_name(self):
-        if self.for_update:
-            return "column_onupdate"
-        else:
-            return "column_default"
-
-    __visit_name__ = property(_visit_name)
-
     def __repr__(self):
         return "ColumnDefault(%r)" % (self.arg,)
 
@@ -2861,6 +2853,8 @@ class CheckConstraint(ColumnCollectionConstraint):
 
     _allow_multiple_tables = True
 
+    __visit_name__ = "table_or_column_check_constraint"
+
     @_document_text_coercion(
         "sqltext",
         ":class:`.CheckConstraint`",
@@ -2925,13 +2919,9 @@ class CheckConstraint(ColumnCollectionConstraint):
         if table is not None:
             self._set_parent_with_dispatch(table)
 
-    def __visit_name__(self):
-        if isinstance(self.parent, Table):
-            return "check_constraint"
-        else:
-            return "column_check_constraint"
-
-    __visit_name__ = property(__visit_name__)
+    @property
+    def is_column_level(self):
+        return not isinstance(self.parent, Table)
 
     def copy(self, target_table=None, **kw):
         if target_table is not None:
diff --git a/lib/sqlalchemy/sql/visitors.py b/lib/sqlalchemy/sql/visitors.py
index c946bb4ab..77e6b53a8 100644
--- a/lib/sqlalchemy/sql/visitors.py
+++ b/lib/sqlalchemy/sql/visitors.py
@@ -24,7 +24,6 @@ http://techspot.zzzeek.org/2008/01/23/expression-transformations/ .
 """
 
 from collections import deque
-import operator
 
 from .. import exc
 from .. import util
@@ -53,32 +52,26 @@ def _generate_compiler_dispatch(cls):
     """
     visit_name = cls.__visit_name__
 
-    if isinstance(visit_name, util.compat.string_types):
-        # There is an optimization opportunity here because the
-        # the string name of the class's __visit_name__ is known at
-        # this early stage (import time) so it can be pre-constructed.
-        getter = operator.attrgetter("visit_%s" % visit_name)
-
-        def _compiler_dispatch(self, visitor, **kw):
-            try:
-                meth = getter(visitor)
-            except AttributeError:
-                raise exc.UnsupportedCompilationError(visitor, cls)
-            else:
-                return meth(self, **kw)
-
-    else:
-        # The optimization opportunity is lost for this case because the
-        # __visit_name__ is not yet a string. As a result, the visit
-        # string has to be recalculated with each compilation.
-        def _compiler_dispatch(self, visitor, **kw):
-            visit_attr = "visit_%s" % self.__visit_name__
-            try:
-                meth = getattr(visitor, visit_attr)
-            except AttributeError:
-                raise exc.UnsupportedCompilationError(visitor, cls)
-            else:
-                return meth(self, **kw)
+    if not isinstance(visit_name, util.compat.string_types):
+        raise exc.InvalidRequestError(
+            "__visit_name__ on class %s must be a string at the class level"
+            % cls.__name__
+        )
+
+    code = (
+        "def _compiler_dispatch(self, visitor, **kw):\n"
+        "    try:\n"
+        "        meth = visitor.visit_%(name)s\n"
+        "    except AttributeError:\n"
+        "        util.raise_from_cause(\n"
+        "            exc.UnsupportedCompilationError(visitor, cls))\n"
+        "    else:\n"
+        "        return meth(self, **kw)\n"
+    ) % {"name": visit_name}
+
+    _compiler_dispatch = langhelpers._exec_code_in_env(
+        code, {"exc": exc, "cls": cls, "util": util}, "_compiler_dispatch"
+    )
 
     _compiler_dispatch.__doc__ = """Look for an attribute named "visit_"
         + self.__visit_name__ on the visitor, and call it with the same