by Damyon Wiese.
Hi Michael,
The error you have reported is unusual - because the code removes that index before it removes the column, so it should not be happening. I tested the upgrade on Oracle and did not have any issues. If you can retest using the Moodle 2.5rc1 build that would be helpful and if you continue to have errors please report it as a bug in the tracker.
Thanks, Damyon