[Zope] KeyError

[Asad Habib]

Hello. I am calling a DTML method via a link and inside this method a Z
SQL method is called. When this method is called, Zope flags me with a
KeyError. The error is as follows:

Site Error

An error was encountered while publishing this resource.

Error Type: KeyError
Error Value: 0

Troubleshooting Suggestions
This resource may be trying to reference a  nonexistent object or variable
0.

The URL may be incorrect.
The parameters passed to this resource may be incorrect.
A resource that this resource relies on may be encountering  an error.

For more detailed information about the error, please  refer to the error
log. If the error persists please contact the site maintainer.  Thank you
for your patience.

The error log gives the following traceback:

Traceback (innermost last):
  Module ZPublisher.Publish, line 100, in publish
  Module ZPublisher.mapply, line 88, in mapply
  Module ZPublisher.Publish, line 40, in call_object
  Module OFS.DTMLMethod, line 130, in __call__
   - <DTMLMethod instance at 3a4f5f0>
   - URL:
http://nameofmachine/edit_data/manage_main
   - Physical Path: /edit_data
  Module DocumentTemplate.DT_String, line 474, in __call__
  Module DocumentTemplate.DT_In, line 676, in renderwob
  Module AccessControl.ImplPython, line 161, in guarded_getitem
  Module AccessControl.ZopeGuards, line 67, in guarded_getitem
  Module Shared.DC.ZRDB.DA, line 487, in __getitem__
  Module Shared.DC.ZRDB.Aqueduct, line 313, in __getitem__
KeyError: 0


edit_data is the DTML method invoked via a link and the name of the Z SQL
method is retrieve_names_sql and its definition is as follows:

SELECT last_name, first_name, middle_name FROM test
WHERE id = <dtml-var "REQUEST.SESSION.get('userId')">

The Z SQL method is called using the following statement:

<dtml-call "retrieve_names_sql(REQUEST, _)">


Any help would be greatly appreciated. Thanks.

- Asad