fix selectable columns warning

sqlalchemy_utils/functions/orm.py

@@ -462,7 +462,10 @@ def get_columns(mixed):
         instance or an alias of any of these objects
     """
     if isinstance(mixed, sa.sql.selectable.Selectable):
-        return mixed.c
+        try:
+            return mixed.selected_columns
+        except AttributeError:  # SQLAlchemy <1.4
+            return mixed.c
     if isinstance(mixed, sa.orm.util.AliasedClass):
         return sa.inspect(mixed).mapper.columns
     if isinstance(mixed, sa.orm.Mapper):

sqlalchemy_utils/view.py

@@ -2,6 +2,8 @@
 from sqlalchemy.ext import compiler
 from sqlalchemy.schema import DDLElement, PrimaryKeyConstraint
 
+from sqlalchemy_utils.functions import get_columns
+
 
 class CreateView(DDLElement):
     def __init__(self, name, selectable, materialized=False):
@@ -55,13 +57,13 @@ def create_table_from_selectable(
             key=aliases.get(c.name, c.name),
             primary_key=c.primary_key
         )
-        for c in selectable.c
+        for c in get_columns(selectable)
     ] + indexes
     table = sa.Table(name, metadata, *args)
 
-    if not any([c.primary_key for c in selectable.c]):
+    if not any([c.primary_key for c in get_columns(selectable)]):
         table.append_constraint(
-            PrimaryKeyConstraint(*[c.name for c in selectable.c])
+            PrimaryKeyConstraint(*[c.name for c in get_columns(selectable)])
         )
     return table