> How would an index be helpful in processing a "x & ? = 0" WHERE clause term? What algorithm do you propose? Wouldn't you then only need to execute the test once per each unique value of x? Go through the index in order, when x changes test the new x. Then you can either say "include every row until x changes" or "ignore every row until x changes" On a simple test like this then it might not save much, but the more expensive the test, and the fewer distinct values of x then the more useful that would be. (That or I'm missing something obvious)