MySQLdb connection Objects contain cyclic references which keep the
connection objectfrom beeing closed and dealloced by pythons reference
counting garbage collector at function exit. The connection object contains
support for the cycle detecting garbage collector but it takes an unknowen
tome untill the cycle detecting garbage collector kicks in which means you
have an unusable but still open connection to your database for an undefined
time. This can be avoided by structuring your code carefully to allways call
connection.close() before returning from a function but doing so is very
unpythonic.

This patch migrates the problem by changing the cyclic references to weak
references which allow reference counting to work as desired. Probably
restructuring of the classes to avoid cyclic references would be a better
solution.

Code demonstrating the problem:

import MySQLdb

def userPassOk(user, passwd):
    db = MySQLdb.connect(...)
    c = db.cursor()
    c.execute("select USER_NAME, USER_PASSWORD from AV_USER WHERE USER_NAME = '%s'" % user)
    print c.fetchall()
    c.close()
    #db.close()

if __name__ == '__main__':
    for i in range(20000):
        print i, 
        userPassOk(user="guest", passwd='guest')


  --md@hudora.de

--- /usr/local/lib/python2.3/site-packages/MySQLdb/connections.py.orig	Mon Nov  3 23:46:07 2003
+++ /usr/local/lib/python2.3/site-packages/MySQLdb/connections.py	Mon Nov  3 23:56:22 2003
@@ -12,6 +12,7 @@
      NotSupportedError, ProgrammingError
 import types, _mysql
 
+from weakref import proxy
 
 def defaulterrorhandler(connection, cursor, errorclass, errorvalue):
     """
@@ -113,9 +114,9 @@
             conv[FIELD_TYPE.STRING] = u
             conv[FIELD_TYPE.VAR_STRING] = u
         self._make_connection(args, kwargs2)
-        self.converter[types.StringType] = self.string_literal
+        self.converter[types.StringType] = proxy(self.string_literalPY)
         if hasattr(types, 'UnicodeType'):
-            self.converter[types.UnicodeType] = self.unicode_literal
+            self.converter[types.UnicodeType] = proxy(self.unicode_literal)
         self._transactional = self.server_capabilities & CLIENT.TRANSACTIONS
         self.messages = []
         
@@ -164,6 +165,10 @@
 
         """
         return self.escape(o, self.converter)
+
+    def string_literalPY(self, obj):
+        """use string_literal(obj) instead!"""
+        self.string_literal(obj)
 
     def unicode_literal(self, u, dummy=None):
         """