For some reason I thought ZSQL method calls were atomic, but they appear otherwise.
Using an eGenix mxODBC Database Connection at /Database/PoPy_database_connection to a SQL Server 2000 back end, I have created a Python script to write SQL commands and feed them in one large string:
UPDATE equip SET workstation=1 WHERE eq_id=39315;
UPDATE node SET node='M28057' WHERE node_id=13451;
UPDATE materiel SET mat_nm='mm-M28057-H-01', owner='mmaslak', datetime='2006/04/24 15:09:07.611 GMT-5' WHERE mat_id=39315;
This all gets sent as one string to a ZSQL method where the first two commands execute, but the third fails because it doesn't like the datetime string, which indeed fails when I try it alone in the PoPy connection. Why, then doesn't the whole thing fail like I might expect?
When I wrap the call in a 'begin transaction … commit', it becomes atomic. Nothing changes in the database if part of it fails. Great.
But failure is not detectable by the Python script. I have used try/except and if/else blocks to ascertain failure. It thinks a non-commit is AOK, not an exception. Is this function of the eGenix ODBC? Of MS SQL Server 2K? Zope/ZSQL/Python?
How can I detect failure or success in the Python script and still maintain atomicity? Do I need to program by contract?
Michael Maslak, Jr.
Associate Software Engineer
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