disable all raiseload within the unit of work process.

The unit of work process now turns off all "lazy='raise'" behavior
altogether when a flush is proceeding.  While there are areas where the UOW
is sometimes loading things that aren't ultimately needed, the lazy="raise"
strategy is not helpful here as the user often does not have much control
or visibility into the flush process.

Fixes: #5984
Change-Id: I23f2e332a5faa5c7c29823c9be9434d129676a5a

2 files changed, 13 insertions, 2 deletions

diff --git a/lib/sqlalchemy/orm/dependency.py b/lib/sqlalchemy/orm/dependency.py
index 5a329b28c..85f6b68ff 100644
--- a/lib/sqlalchemy/orm/dependency.py
+++ b/lib/sqlalchemy/orm/dependency.py
@@ -229,6 +229,11 @@ class DependencyProcessor(object):
         if not isdelete or self.passive_deletes:
             passive = attributes.PASSIVE_NO_INITIALIZE
         elif self.direction is MANYTOONE:
+            # here, we were hoping to optimize having to fetch many-to-one
+            # for history and ignore it, if there's no further cascades
+            # to take place.  however there are too many less common conditions
+            # that still take place and tests in test_relationships /
+            # test_cascade etc. will still fail.
             passive = attributes.PASSIVE_NO_FETCH_RELATED
         else:
             passive = attributes.PASSIVE_OFF
diff --git a/lib/sqlalchemy/orm/unitofwork.py b/lib/sqlalchemy/orm/unitofwork.py
index c293d90cb..1fb1c10ac 100644
--- a/lib/sqlalchemy/orm/unitofwork.py
+++ b/lib/sqlalchemy/orm/unitofwork.py
@@ -254,7 +254,9 @@ class UOWTransaction(object):
                 history = impl.get_history(
                     state,
                     state.dict,
-                    attributes.PASSIVE_OFF | attributes.LOAD_AGAINST_COMMITTED,
+                    attributes.PASSIVE_OFF
+                    | attributes.LOAD_AGAINST_COMMITTED
+                    | attributes.NO_RAISE,
                 )
                 if history and impl.uses_objects:
                     state_history = history.as_state()
@@ -266,7 +268,11 @@ class UOWTransaction(object):
             # TODO: store the history as (state, object) tuples
             # so we don't have to keep converting here
             history = impl.get_history(
-                state, state.dict, passive | attributes.LOAD_AGAINST_COMMITTED
+                state,
+                state.dict,
+                passive
+                | attributes.LOAD_AGAINST_COMMITTED
+                | attributes.NO_RAISE,
             )
             if history and impl.uses_objects:
                 state_history = history.as_state()