upgrade deferred loader to regular loader if refresh_state

Fixed issue where deferred polymorphic loading of attributes from a
joined-table inheritance subclass would fail to populate the attribute
correctly if the :func:`_orm.load_only` option were used to originally
exclude that attribute, in the case where the load_only were descending
from a relationship loader option.  The fix allows that other valid options
such as ``defer(..., raiseload=True)`` etc. still function as expected.

Fixes: #7304
Change-Id: I58b7ce7c450bcc52d2f0c9bfbcb4d747463ee9b2

1 files changed, 20 insertions, 1 deletions

diff --git a/lib/sqlalchemy/orm/strategies.py b/lib/sqlalchemy/orm/strategies.py
index 2a283caad..71c4a6976 100644
--- a/lib/sqlalchemy/orm/strategies.py
+++ b/lib/sqlalchemy/orm/strategies.py
@@ -382,7 +382,26 @@ class DeferredColumnLoader(LoaderStrategy):
         # dictionary.  Normally, the DeferredColumnLoader.setup_query()
         # sets up that data in the "memoized_populators" dictionary
         # and "create_row_processor()" here is never invoked.
-        if not self.is_class_level:
+
+        if (
+            context.refresh_state
+            and context.query._compile_options._only_load_props
+            and self.key in context.query._compile_options._only_load_props
+        ):
+            self.parent_property._get_strategy(
+                (("deferred", False), ("instrument", True))
+            ).create_row_processor(
+                context,
+                query_entity,
+                path,
+                loadopt,
+                mapper,
+                result,
+                adapter,
+                populators,
+            )
+
+        elif not self.is_class_level:
             if self.raiseload:
                 set_deferred_for_local_state = (
                     self.parent_property._raise_column_loader