Hi Robert

I don't think there's any official documentation. There's my article and another by Oswald Petersen (son?). Its easy enough to prove. Use a large table, set an optimzable filter that returns few records and browse. To see the problem, build a simple form with a grid that shows 10 records, set the same filter in the form and run the form.

Someone sent me a quote from the Hacker's guide that I keep around...

"SET KEY is similar to SET FILTER, except that it uses the current index order. And except that, used with grids (where filters aren't optimized), SET KEY is much, much, much faster than the equivalent filter."