[storm] No exception raised when hitting database locking error

[james at jamesh.id.au]

On Mon, Dec 20, 2010 at 8:08 AM, Steve Kieu <msh.computing at gmail.com> wrote:
>
>> It isn't unusual for serialisation errors to be reported prior to
>> commit: the database usually reports them as soon as it detects the
>> problem.  The traceback from the error you saw probably tells you
>> where it occurred.  Try wrapping your try/except block around the
>> entire transaction logic rather than just the commit() call.
>>
>> If you're using PostgreSQL, the
>> psycopg2.extensions.TransactionRollbackError exception should cover
>> the cases you're interested in.
>>
>
> Yes you are correct, I got the exception now if I wrap the entire block.
>
> Error I GOT YOU : could not serialize access due to concurrent update
>
> <class 'psycopg2.extensions.TransactionRollbackError'>
>
> Should I rollback and try again or just try to run the block again? It may
> not improve the performance as I have to do it all again <sigh>

If your transaction fails, then none of the changes made during the
transaction will have been recorded.  So replaying the entire
transaction is generally what you'd want to do.

If you are performing many inserts or updates and want to maximise
performance, you might be best off structuring your code so you can
easily tweak how much work you do in each transaction.  You can then
adjust that setting to maximise the performance.  Depending on what
you're doing, updating 100 or 1000 rows in each transaction might be a
good place to start.

James.