- Fixed bug where a newly inserted instance that is rolled back

would still potentially cause persistence conflicts on the next
transaction, because the instance would not be checked that it
was expired.   This fix will resolve a large class of cases that
erronously cause the "New instance with identity X conflicts with
persistent instance Y" error.
fixes #3677

2 files changed, 31 insertions, 16 deletions

diff --git a/lib/sqlalchemy/orm/persistence.py b/lib/sqlalchemy/orm/persistence.py
index b9a1f9df9..a5e0d9d95 100644
--- a/lib/sqlalchemy/orm/persistence.py
+++ b/lib/sqlalchemy/orm/persistence.py
@@ -295,22 +295,24 @@ def _organize_states_for_save(base_mapper, states, uowtransaction):
             instance = \
                 uowtransaction.session.identity_map[instance_key]
             existing = attributes.instance_state(instance)
-            if not uowtransaction.is_deleted(existing):
-                raise orm_exc.FlushError(
-                    "New instance %s with identity key %s conflicts "
-                    "with persistent instance %s" %
-                    (state_str(state), instance_key,
-                     state_str(existing)))
-
-            base_mapper._log_debug(
-                "detected row switch for identity %s.  "
-                "will update %s, remove %s from "
-                "transaction", instance_key,
-                state_str(state), state_str(existing))
-
-            # remove the "delete" flag from the existing element
-            uowtransaction.remove_state_actions(existing)
-            row_switch = existing
+
+            if not uowtransaction.was_already_deleted(existing):
+                if not uowtransaction.is_deleted(existing):
+                    raise orm_exc.FlushError(
+                        "New instance %s with identity key %s conflicts "
+                        "with persistent instance %s" %
+                        (state_str(state), instance_key,
+                         state_str(existing)))
+
+                base_mapper._log_debug(
+                    "detected row switch for identity %s.  "
+                    "will update %s, remove %s from "
+                    "transaction", instance_key,
+                    state_str(state), state_str(existing))
+
+                # remove the "delete" flag from the existing element
+                uowtransaction.remove_state_actions(existing)
+                row_switch = existing
 
         if (has_identity or row_switch) and mapper.version_id_col is not None:
             update_version_id = mapper._get_committed_state_attr_by_column(
diff --git a/lib/sqlalchemy/orm/unitofwork.py b/lib/sqlalchemy/orm/unitofwork.py
index 8b4ae64bb..f3e39d9b5 100644
--- a/lib/sqlalchemy/orm/unitofwork.py
+++ b/lib/sqlalchemy/orm/unitofwork.py
@@ -16,6 +16,7 @@ organizes them in order of dependency, and executes.
 from .. import util, event
 from ..util import topological
 from . import attributes, persistence, util as orm_util
+from . import exc as orm_exc
 import itertools
 
 
@@ -155,6 +156,18 @@ class UOWTransaction(object):
     def has_work(self):
         return bool(self.states)
 
+    def was_already_deleted(self, state):
+        """return true if the given state is expired and was deleted
+        previously.
+        """
+        if state.expired:
+            try:
+                state._load_expired(state, attributes.PASSIVE_OFF)
+            except orm_exc.ObjectDeletedError:
+                self.session._remove_newly_deleted([state])
+                return True
+        return False
+
     def is_deleted(self, state):
         """return true if the given state is marked as deleted
         within this uowtransaction."""