I have an Oracle table "T" with 3 columns A,B and C. A & B are indexed, C's not. I excuted the following query:
UPDATE T SET C='Hello' WHERE A='a' AND B='b'
It took 30s to complete knowing that there're about 400 rows in my table. It's ridiculous! I tried to remove the indexes on columns A & B and the query completes much more faster (about 3s). Why does updating a non-indexed column take so much time? Anybody has somes ideas? Thanks a lot!