--- a/server/schemahooks.py	Sat Aug 01 01:13:39 2009 +0200
+++ b/server/schemahooks.py	Sat Aug 01 01:16:19 2009 +0200
@@ -51,7 +51,7 @@
     column = SQL_PREFIX + rtype
     try:
         session.system_sql(str('ALTER TABLE %s ADD COLUMN %s integer'
-                               % (table, column)))
+                               % (table, column)), rollback_on_failure=False)
         session.info('added column %s to table %s', column, table)
     except:
         # silent exception here, if this error has not been raised because the
@@ -128,7 +128,7 @@
         session.pool.source('system').drop_index(session, table, column)
         try:
             session.system_sql('ALTER TABLE %s DROP COLUMN %s'
-                               % (table, column))
+                               % (table, column), rollback_on_failure=False)
             self.info('dropped column %s from table %s', column, table)
         except Exception, ex:
             # not supported by sqlite for instance
@@ -410,7 +410,8 @@
         column = SQL_PREFIX + rtype
         try:
             session.system_sql(str('ALTER TABLE %s ADD COLUMN %s %s'
-                                   % (table, column, attrtype)))
+                                   % (table, column, attrtype)),
+                               rollback_on_failure=False)
             self.info('added column %s to table %s', table, column)
         except Exception, ex:
             # the column probably already exists. this occurs when
@@ -722,7 +723,7 @@
                                             creating=False)
             sql = adbh.sql_change_col_type(table, column, coltype, card != '1')
             try:
-                session.system_sql(sql)
+                session.system_sql(sql, rollback_on_failure=False)
                 self.info('altered column %s of table %s: now VARCHAR(%s)',
                           column, table, self._cstr.max)
             except Exception, ex:
@@ -761,7 +762,8 @@
         if cstrtype == 'SizeConstraint':
             try:
                 self.session.system_sql('ALTER TABLE %s ALTER COLUMN %s TYPE TEXT'
-                                        % (table, column))
+                                        % (table, column),
+                                        rollback_on_failure=False)
                 self.info('altered column %s of table %s: now TEXT',
                           column, table)
             except Exception, ex:

--- a/server/sources/native.py	Sat Aug 01 01:13:39 2009 +0200
+++ b/server/sources/native.py	Sat Aug 01 01:16:19 2009 +0200
@@ -432,7 +432,7 @@
             sql = self.sqlgen.delete('%s_relation' % rtype, attrs)
         self.doexec(session, sql, attrs)
 
-    def doexec(self, session, query, args=None):
+    def doexec(self, session, query, args=None, rollback=True):
         """Execute a query.
         it's a function just so that it shows up in profiling
         """
@@ -445,11 +445,12 @@
         except Exception, ex:
             self.critical("sql: %r\n args: %s\ndbms message: %r",
                           query, args, ex.args[0])
-            try:
-                session.pool.connection(self.uri).rollback()
-                self.critical('transaction has been rollbacked')
-            except:
-                pass
+            if rollback:
+                try:
+                    session.pool.connection(self.uri).rollback()
+                    self.critical('transaction has been rollbacked')
+                except:
+                    pass
             raise
         return cursor