I have inherited a database which seems very liberal in the use of indexes. On some tables there are up to 9 indexes, several which are using varchars in composite indexes. I was alarmed when I saw the disk space usage of several of these indexes. The database has over 4000 indexes on 600+ tables. I may not have a call in reducing this, but is there a good rule of thumb on how many indexes to use, and at what point you actually incur so much overhead you lose performance gains by having the index?
thanks!