From e1ceee15cd7e5692513ac83716b3201a47a0272e Mon Sep 17 00:00:00 2001
From: Mike Bayer <mike_mp@zzzcomputing.com>
Date: Sat, 6 Jan 2007 03:33:53 +0000
Subject: [PATCH] - added an error message if you actually try to modify
 primary key values on an entity and then flush it.

---
 CHANGES                      |  2 ++
 lib/sqlalchemy/orm/mapper.py |  5 ++++-
 test/orm/unitofwork.py       | 19 +++++++++++++++++++
 3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/CHANGES b/CHANGES
index 798d33fac0..423a47e7c8 100644
--- a/CHANGES
+++ b/CHANGES
@@ -24,6 +24,8 @@ required for firebird, not a bad idea for others [ticket:408]
 - default "timezone" setting is now False.  this corresponds to Python's datetime
 behavior as well as Postgres' timestamp/time types (which is the only timezone-sensitive
 dialect at the moment) [ticket:414]
+- added an error message if you actually try to modify primary key values on an entity
+and then flush it.  
 
 0.3.3
 - string-based FROM clauses fixed, i.e. select(..., from_obj=["sometext"])
diff --git a/lib/sqlalchemy/orm/mapper.py b/lib/sqlalchemy/orm/mapper.py
index 67ca75bb3d..b6ff096169 100644
--- a/lib/sqlalchemy/orm/mapper.py
+++ b/lib/sqlalchemy/orm/mapper.py
@@ -841,7 +841,10 @@ class Mapper(object):
                 if self.__should_log_debug:
                     self.__log_debug("detected row switch for identity %s.  will update %s, remove %s from transaction" % (instance_key, mapperutil.instance_str(obj), mapperutil.instance_str(existing)))
                 uowtransaction.unregister_object(existing)
-            
+            if has_identity(obj):
+                if obj._instance_key != instance_key:
+                    raise exceptions.FlushError("Can't change the identity of instance %s in session (existing identity: %s; new identity: %s)" % (mapperutil.instance_str(obj), obj._instance_key, instance_key))
+                
         inserted_objects = util.Set()
         updated_objects = util.Set()
         
diff --git a/test/orm/unitofwork.py b/test/orm/unitofwork.py
index ed3b9fca1d..c1f885bb0e 100644
--- a/test/orm/unitofwork.py
+++ b/test/orm/unitofwork.py
@@ -3,6 +3,7 @@ from sqlalchemy import *
 import testbase
 import pickleable
 from sqlalchemy.orm.mapper import global_extensions
+from sqlalchemy.orm import util as ormutil
 from sqlalchemy.ext.sessioncontext import SessionContext
 import sqlalchemy.ext.assignmapper as assignmapper
 from tables import *
@@ -403,6 +404,24 @@ class PKTest(UnitOfWorkTest):
         e.data = 'some more data'
         ctx.current.flush()
 
+    def testpksimmutable(self):
+        class Entry(object):
+            pass
+        mapper(Entry, table)
+        e = Entry()
+        e.multi_id=5
+        e.multi_rev=5
+        e.name='somename'
+        ctx.current.flush()
+        e.multi_rev=6
+        e.name = 'someothername'
+        try:
+            ctx.current.flush()
+            assert False
+        except exceptions.FlushError, fe:
+            assert str(fe) == "Can't change the identity of instance Entry@%s in session (existing identity: (%s, (5, 5), None); new identity: (%s, (5, 6), None))" % (hex(id(e)), repr(e.__class__), repr(e.__class__))
+            
+            
 class ForeignPKTest(UnitOfWorkTest):
     """tests mapper detection of the relationship direction when parent/child tables are joined on their
     primary keys"""
-- 
2.47.2