3 files changed, 44 insertions, 1 deletions
diff --git a/lib/sqlalchemy/sql/base.py b/lib/sqlalchemy/sql/base.py
index d9f05e823..6d65d9061 100644
--- a/lib/sqlalchemy/sql/base.py
+++ b/lib/sqlalchemy/sql/base.py
@@ -15,6 +15,7 @@ import operator
 import re
 
 from . import roles
+from . import visitors
 from .traversals import HasCacheKey  # noqa
 from .traversals import HasCopyInternals  # noqa
 from .traversals import MemoizedHasCacheKey  # noqa
@@ -1575,6 +1576,23 @@ def _bind_or_error(schemaitem, msg=None):
     return bind
 
 
+def _entity_namespace(entity):
+    """Return the nearest .entity_namespace for the given entity.
+
+    If not immediately available, does an iterate to find a sub-element
+    that has one, if any.
+
+    """
+    try:
+        return entity.entity_namespace
+    except AttributeError:
+        for elem in visitors.iterate(entity):
+            if hasattr(elem, "entity_namespace"):
+                return elem.entity_namespace
+        else:
+            raise
+
+
 def _entity_namespace_key(entity, key):
     """Return an entry from an entity_namespace.
 
@@ -1584,8 +1602,8 @@ def _entity_namespace_key(entity, key):
 
     """
 
-    ns = entity.entity_namespace
     try:
+        ns = _entity_namespace(entity)
         return getattr(ns, key)
     except AttributeError as err:
         util.raise_(
diff --git a/lib/sqlalchemy/sql/elements.py b/lib/sqlalchemy/sql/elements.py
index e27b97802..416a4e82e 100644
--- a/lib/sqlalchemy/sql/elements.py
+++ b/lib/sqlalchemy/sql/elements.py
@@ -300,6 +300,13 @@ class ClauseElement(
             f = f._is_clone_of
         return s
 
+    @property
+    def entity_namespace(self):
+        raise AttributeError(
+            "This SQL expression has no entity namespace "
+            "with which to filter from."
+        )
+
     def __getstate__(self):
         d = self.__dict__.copy()
         d.pop("_is_clone_of", None)
@@ -4664,6 +4671,13 @@ class ColumnClause(
         # expect the columns of tables and subqueries to be leaf nodes.
         return []
 
+    @property
+    def entity_namespace(self):
+        if self.table is not None:
+            return self.table.entity_namespace
+        else:
+            return super(ColumnClause, self).entity_namespace
+
     @HasMemoized.memoized_attribute
     def _from_objects(self):
         t = self.table
diff --git a/lib/sqlalchemy/sql/functions.py b/lib/sqlalchemy/sql/functions.py
index 02ed55100..0aa870ce4 100644
--- a/lib/sqlalchemy/sql/functions.py
+++ b/lib/sqlalchemy/sql/functions.py
@@ -15,6 +15,7 @@ from . import roles
 from . import schema
 from . import sqltypes
 from . import util as sqlutil
+from .base import _entity_namespace
 from .base import ColumnCollection
 from .base import Executable
 from .base import Generative
@@ -618,6 +619,16 @@ class FunctionElement(Executable, ColumnElement, FromClause, Generative):
         else:
             return super(FunctionElement, self).self_group(against=against)
 
+    @property
+    def entity_namespace(self):
+        """overrides FromClause.entity_namespace as functions are generally
+        column expressions and not FromClauses.
+
+        """
+        # ideally functions would not be fromclauses but we failed to make
+        # this adjustment in 1.4
+        return _entity_namespace(self.clause_expr)
+
 
 class FunctionAsBinary(BinaryExpression):
     _traverse_internals = [