Implement relationship to AliasedClass; deprecate non primary mappers

Implemented a new feature whereby the :class:`.AliasedClass` construct can
now be used as the target of a :func:`.relationship`.  This allows the
concept of "non primary mappers" to no longer be necessary, as the
:class:`.AliasedClass` is much easier to configure and automatically inherits
all the relationships of the mapped class, as well as preserves the
ability for loader options to work normally.

- introduce new name for mapped_table, "persist_selectable".  this is
the selectable that selects against the local mapper and its superclasses,
but does not include columns local only to subclasses.

- relationship gains "entity" which is the mapper or aliasedinsp.

- clarfiy name "entity" vs. "query_entity" in loader strategies.

Fixes: #4423
Fixes: #4422
Fixes: #4421
Fixes: #3348

Change-Id: Ic3609b43dc4ed115006da9ad9189e574dc0c72d9

1 files changed, 5 insertions, 5 deletions

diff --git a/lib/sqlalchemy/ext/declarative/base.py b/lib/sqlalchemy/ext/declarative/base.py
index 269cfce00..80cd23bc8 100644
--- a/lib/sqlalchemy/ext/declarative/base.py
+++ b/lib/sqlalchemy/ext/declarative/base.py
@@ -163,7 +163,7 @@ class _MapperConfig(object):
         # dict_ will be a dictproxy, which we can't write to, and we need to!
         self.dict_ = dict(dict_)
         self.classname = classname
-        self.mapped_table = None
+        self.persist_selectable = None
         self.properties = util.OrderedDict()
         self.declared_columns = set()
         self.column_copies = {}
@@ -584,7 +584,7 @@ class _MapperConfig(object):
         elif self.inherits:
             inherited_mapper = _declared_mapping_info(self.inherits)
             inherited_table = inherited_mapper.local_table
-            inherited_mapped_table = inherited_mapper.mapped_table
+            inherited_persist_selectable = inherited_mapper.persist_selectable
 
             if table is None:
                 # single table inheritance.
@@ -611,10 +611,10 @@ class _MapperConfig(object):
                         )
                     inherited_table.append_column(c)
                     if (
-                        inherited_mapped_table is not None
-                        and inherited_mapped_table is not inherited_table
+                        inherited_persist_selectable is not None
+                        and inherited_persist_selectable is not inherited_table
                     ):
-                        inherited_mapped_table._refresh_for_new_column(c)
+                        inherited_persist_selectable._refresh_for_new_column(c)
 
     def _prepare_mapper_arguments(self):
         properties = self.properties