aliased column overrides don't override

[Former user]

When using MySQL 4 table reflection with assign_mapper and a table column override, updating an object causes the following error:

sqlalchemy.exceptions.ConcurrentModificationError: Updated rowcount 0 does not match number of objects updated 1

The table setup looks like:

user_table = Table('ur', sac.get_metadata('default'), 
                   Column('cs_rid', Integer, primary_key=True, key='id'), 
                   autoload=True)

class User(object):
    pass

assign_mapper(sac.session_context, User, user_table)

Upon removing the primary_key statement from the Column, the exception disappears.

[jek]

When aliased user columns (key=) are processed after autoload, ColumnCollection.add includes them via column.key, alongside the originals which had column.key == collumn.name.

This affects all autoloads, not related to mysql reflection in particular.

[jek]

A fix for the case above is straightforward, but more thought needs to go into what the expected behavior is with regard to existing autoloaded keys and constraints, especially if the override specifies different pk/fk keying than the original.

[Mike Bayer]

im happy with just the "key" part of this for now; committed in changeset:2909.

oh i guess we'll leave the rest to 0.4 then....

[Mike Bayer]

here's a patch, make _link_to_name public too:

Index: lib/sqlalchemy/schema.py
===================================================================
--- lib/sqlalchemy/schema.py    (revision 5527)
+++ lib/sqlalchemy/schema.py    (working copy)
@@ -769,7 +769,7 @@

     __visit_name__ = 'foreign_key'

-    def __init__(self, column, constraint=None, use_alter=False, name=None, onupdate=None, ondelete=None, deferrable=None, initially=None):
+    def __init__(self, column, constraint=None, use_alter=False, name=None, onupdate=None, ondelete=None, deferrable=None, initially=None, _link_to_name=False):
         """
         Construct a column-level FOREIGN KEY.

@@ -812,6 +812,7 @@
         self.ondelete = ondelete
         self.deferrable = deferrable
         self.initially = initially
+        self._link_to_name = _link_to_name

     def __repr__(self):
         return "ForeignKey(%r)" % self._get_colspec()
@@ -888,10 +889,16 @@
                 else:
                     _column = table.c[colname](colname)
             except KeyError, e:
-                raise exc.NoReferencedColumnError(
-                    "Could not create ForeignKey '%s' on table '%s': "
-                    "table '%s' has no column named '%s'" % (
-                    self._colspec, parenttable.name, table.name, str(e)))
+                _column = None
+                if self._link_to_name:
+                    for c in table.c:
+                        if c.name == colname:
+                            _column = c
+                if not _column:
+                    raise exc.NoReferencedColumnError(
+                        "Could not create ForeignKey '%s' on table '%s': "
+                        "table '%s' has no column named '%s'" % (
+                        self._colspec, parenttable.name, table.name, e))

         elif hasattr(self._colspec, '__clause_element__'):
             _column = self._colspec.__clause_element__()
@@ -1191,7 +1198,7 @@
     """
     __visit_name__ = 'foreign_key_constraint'

-    def __init__(self, columns, refcolumns, name=None, onupdate=None, ondelete=None, use_alter=False, deferrable=None, initially=None):
+    def __init__(self, columns, refcolumns, name=None, onupdate=None, ondelete=None, use_alter=False, deferrable=None, initially=None, _link_to_name=False):
         """Construct a composite-capable FOREIGN KEY.

         columns
@@ -1235,6 +1242,7 @@
         self.elements = util.OrderedSet()
         self.onupdate = onupdate
         self.ondelete = ondelete
+        self._link_to_name = _link_to_name
         if self.name is None and use_alter:
             raise exc.ArgumentError("Alterable ForeignKey/ForeignKeyConstraint requires a name")
         self.use_alter = use_alter
@@ -1247,7 +1255,7 @@
                 self.append_element(c, r)

     def append_element(self, col, refcol):
-        fk = ForeignKey(refcol, constraint=self, name=self.name, onupdate=self.onupdate, ondelete=self.ondelete, use_alter=self.use_alter)
+        fk = ForeignKey(refcol, constraint=self, name=self.name, onupdate=self.onupdate, ondelete=self.ondelete, use_alter=self.use_alter, _link_to_name=self._link_to_name)
         fk._set_parent(self.table.c[col](col))
         self._append_fk(fk)

Index: lib/sqlalchemy/databases/sqlite.py
===================================================================
--- lib/sqlalchemy/databases/sqlite.py  (revision 5527)
+++ lib/sqlalchemy/databases/sqlite.py  (working copy)
@@ -522,7 +522,7 @@
             if refspec not in fk[1](1):
                 fk[1](1).append(refspec)
         for name, value in fks.iteritems():
-            table.append_constraint(schema.ForeignKeyConstraint(value[0](0), value[1](1)))
+            table.append_constraint(schema.ForeignKeyConstraint(value[0](0), value[1](1), _link_to_name=True))
         # check for UNIQUE indexes
         c = connection.execute("%sindex_list(%s)" % (pragma, qtable))
         unique_indexes = []

[Mike Bayer]

reflected foreign keys target by column name only in 83a756c5415fad752933ed7f1aff69d2a184d618.

[Mike Bayer]

Removing milestone: 0.5.0 (automated comment)