Question

I have a query that needs to go on EACH AND EVERY record in a table. I do have a condition WHERE LENGTH(f1)>2
Still, it should do a full table scan, but it seems to be using an index, which makes it actually slower.
How do I make a query not to use specific index (namely, the one on f1).

Answer 1

Use index hints:

SELECT ...
FROM sometable
IGNORE INDEX (`name_of_index`)
WHERE ...