[Sqlalchemy-tickets] Issue #3006: orm DELETE not using DB-persited PK in the event of PK change (zzzeek/sqlalchemy)

[Mike B. <iss...@bi...>]

New issue 3006: orm DELETE not using DB-persited PK in the event of PK change
https://bitbucket.org/zzzeek/sqlalchemy/issue/3006/orm-delete-not-using-db-persited-pk-in-the

Mike Bayer:


```
#!python

from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()

class A(Base):
    __tablename__ = 'a'

    id = Column(Integer, primary_key=True)

e = create_engine("sqlite://", echo=True)
#e = create_engine('postgresql://scott:tiger@localhost/test', echo=True)

Base.metadata.drop_all(e)
Base.metadata.create_all(e)

sess = Session(e)
a1 = A(id=1)
sess.add(a1)
sess.commit()

a1.id = 2
sess.delete(a1)
sess.commit()
```

note that we will turn on "multi rowcount" checking which seems to have been removed, also psycopg2 supports this now:


```
#!diff

diff --git a/lib/sqlalchemy/dialects/postgresql/psycopg2.py b/lib/sqlalchemy/dialects/postgresql/psycopg2.py
index 099ddf0..ac17706 100644
--- a/lib/sqlalchemy/dialects/postgresql/psycopg2.py
+++ b/lib/sqlalchemy/dialects/postgresql/psycopg2.py
@@ -347,7 +347,7 @@ class PGDialect_psycopg2(PGDialect):
         supports_unicode_statements = False
 
     default_paramstyle = 'pyformat'
-    supports_sane_multi_rowcount = False
+    supports_sane_multi_rowcount = False  # set to true based on psycopg2 version
     execution_ctx_cls = PGExecutionContext_psycopg2
     statement_compiler = PGCompiler_psycopg2
     preparer = PGIdentifierPreparer_psycopg2
@@ -393,6 +393,9 @@ class PGDialect_psycopg2(PGDialect):
                             is not None
         self._has_native_json = self.psycopg2_version >= (2, 5)
 
+        # http://initd.org/psycopg/docs/news.html#what-s-new-in-psycopg-2-0-9
+        self.supports_sane_multi_rowcount = self.psycopg2_version >= (2, 0, 9)
+
     @classmethod
     def dbapi(cls):
         import psycopg2
diff --git a/lib/sqlalchemy/orm/persistence.py b/lib/sqlalchemy/orm/persistence.py
index 3563198..7a9f3d5 100644
--- a/lib/sqlalchemy/orm/persistence.py
+++ b/lib/sqlalchemy/orm/persistence.py
@@ -702,7 +702,16 @@ def _emit_delete_statements(base_mapper, uowtransaction, cached_connections,
                     stacklevel=12)
                 connection.execute(statement, del_objects)
         else:
-            connection.execute(statement, del_objects)
+            c = connection.execute(statement, del_objects)
+            if connection.dialect.supports_sane_multi_rowcount and \
+                c.rowcount != len(del_objects):
+                raise orm_exc.StaleDataError(
+                    "DELETE statement on table '%s' expected to "
+                    "delete %d row(s); %d were matched." %
+                    (table.description, len(del_objects), c.rowcount)
+                )
+
+
 
 
 def _finalize_insert_update_commands(base_mapper, uowtransaction,

```