use row locking in MySQL newid() [SF#1034211]

Author: Richard Jones

CHANGES.txt

@@ -40,6 +40,7 @@ Fixed:
   discarding of the message
 - mailgw can override the MAIL_DEFAULT_CLASS
 - handle Py2.3+ datetime objects as Date specs (sf bug 971300)
+- use row locking in MySQL newid() (sf bug 1034211)
 
 
 2004-07-21 0.7.6

doc/index.txt

@@ -98,6 +98,7 @@ Christophe Kalt,
 Brian Kelley,
 James Kew,
 Sheila King,
+Michael Klatt,
 Bastian Kleineidam,
 Axel Kollmorgen,
 Detlef Lannert,

roundup/backends/back_mysql.py

@@ -437,8 +437,8 @@ def drop_class_table_key_index(self, cn, key):
     def newid(self, classname):
         ''' Generate a new id for the given class
         '''
-        # get the next ID
-        sql = 'select num from ids where name=%s'%self.arg
+        # get the next ID - "FOR UPDATE" will lock the row for us
+        sql = 'select num from ids where name=%s FOR UPDATE'%self.arg
         self.sql(sql, (classname, ))
         newid = int(self.cursor.fetchone()[0])