Run row value processors up front

as part of a larger series of changes to generalize row-tuples,
RowProxy becomes plain Row and is no longer a "proxy"; the
DBAPI row is now copied directly into the Row when constructed,
result handling occurs at once.

Subsequent changes will break out Row into a new version that
behaves fully a tuple.

Change-Id: I2ffa156afce5d21c38f28e54c3a531f361345dd5

3 files changed, 22 insertions, 23 deletions

diff --git a/lib/sqlalchemy/orm/loading.py b/lib/sqlalchemy/orm/loading.py
index 94a9b8d22..53b901689 100644
--- a/lib/sqlalchemy/orm/loading.py
+++ b/lib/sqlalchemy/orm/loading.py
@@ -358,11 +358,6 @@ def _instance_processor(
     # call overhead.  _instance() is the most
     # performance-critical section in the whole ORM.
 
-    pk_cols = mapper.primary_key
-
-    if adapter:
-        pk_cols = [adapter.columns[c] for c in pk_cols]
-
     identity_class = mapper._identity_class
 
     populators = collections.defaultdict(list)
@@ -488,6 +483,12 @@ def _instance_processor(
     else:
         refresh_identity_key = None
 
+        pk_cols = mapper.primary_key
+
+        if adapter:
+            pk_cols = [adapter.columns[c] for c in pk_cols]
+        tuple_getter = result._tuple_getter(pk_cols, True)
+
     if mapper.allow_partial_pks:
         is_not_primary_key = _none_set.issuperset
     else:
@@ -507,11 +508,7 @@ def _instance_processor(
         else:
             # look at the row, see if that identity is in the
             # session, or we have to create a new one
-            identitykey = (
-                identity_class,
-                tuple([row[column] for column in pk_cols]),
-                identity_token,
-            )
+            identitykey = (identity_class, tuple_getter(row), identity_token)
 
             instance = session_identity_map.get(identitykey)
 
@@ -853,8 +850,10 @@ def _decorate_polymorphic_switch(
 
     polymorphic_instances = util.PopulateDict(configure_subclass_mapper)
 
+    getter = result._getter(polymorphic_on)
+
     def polymorphic_instance(row):
-        discriminator = row[polymorphic_on]
+        discriminator = getter(row)
         if discriminator is not None:
             _instance = polymorphic_instances[discriminator]
             if _instance:
diff --git a/lib/sqlalchemy/orm/strategies.py b/lib/sqlalchemy/orm/strategies.py
index 1f2f65728..d8e5997c1 100644
--- a/lib/sqlalchemy/orm/strategies.py
+++ b/lib/sqlalchemy/orm/strategies.py
@@ -1383,20 +1383,20 @@ class SubqueryLoader(PostLoader):
 
         if self.uselist:
             self._create_collection_loader(
-                context, collections, local_cols, populators
+                context, result, collections, local_cols, populators
             )
         else:
             self._create_scalar_loader(
-                context, collections, local_cols, populators
+                context, result, collections, local_cols, populators
             )
 
     def _create_collection_loader(
-        self, context, collections, local_cols, populators
+        self, context, result, collections, local_cols, populators
     ):
+        tuple_getter = result._tuple_getter(local_cols)
+
         def load_collection_from_subq(state, dict_, row):
-            collection = collections.get(
-                tuple([row[col] for col in local_cols]), ()
-            )
+            collection = collections.get(tuple_getter(row), ())
             state.get_impl(self.key).set_committed_value(
                 state, dict_, collection
             )
@@ -1414,12 +1414,12 @@ class SubqueryLoader(PostLoader):
             populators["eager"].append((self.key, collections.loader))
 
     def _create_scalar_loader(
-        self, context, collections, local_cols, populators
+        self, context, result, collections, local_cols, populators
     ):
+        tuple_getter = result._tuple_getter(local_cols)
+
         def load_scalar_from_subq(state, dict_, row):
-            collection = collections.get(
-                tuple([row[col] for col in local_cols]), (None,)
-            )
+            collection = collections.get(tuple_getter(row), (None,))
             if len(collection) > 1:
                 util.warn(
                     "Multiple rows returned with "
diff --git a/lib/sqlalchemy/orm/util.py b/lib/sqlalchemy/orm/util.py
index 747ec7e65..5f0f41e8d 100644
--- a/lib/sqlalchemy/orm/util.py
+++ b/lib/sqlalchemy/orm/util.py
@@ -297,7 +297,7 @@ def identity_key(*args, **kwargs):
     * ``identity_key(class, row=row, identity_token=token)``
 
       This form is similar to the class/tuple form, except is passed a
-      database result row as a :class:`.RowProxy` object.
+      database result row as a :class:`.Row` object.
 
       E.g.::
 
@@ -307,7 +307,7 @@ first()
         (<class '__main__.MyClass'>, (1, 2), None)
 
       :param class: mapped class (must be a positional argument)
-      :param row: :class:`.RowProxy` row returned by a :class:`.ResultProxy`
+      :param row: :class:`.Row` row returned by a :class:`.ResultProxy`
        (must be given as a keyword arg)
       :param identity_token: optional identity token