I once couldn't convince Oracle planner to use the index at all. It was an index on the one-char status column and all the query had to do was to return the cou

I once couldn't convince Oracle planner to use the index at all. It was an index on the one-char status column and all the query had to do was to return the count of unauthorized rows. Almost always 100% of the rows were authorized, so no matter how many times you ran the analyzer on the table the planner remained convinced that the index was useless and opted for a full table scan instead, wasting minutes. I had to nail down the index with a hint.