On one of the projects we use Oracle 11g database with Label Security enabled. Last week I had a problem with adding NOT NULL constraint to a column.
This query failed due to some NULL values allegedly being present:
That came to me as a surprise as I was pretty sure there were no NULL values - this query returned zero:
The problem was resolved by disabling Label Security policy temporarily:
I'm not familiar enough with Oracle Label Security (OLS) internal workings to explain what was the nature of the problem, but at least I could work around it and move on.
If I find out something more then I'll post an update here.