If I present a user with a table of results from a database which only displays the first 1000 rows, what does the user expect when they re-sort the table?  Do they expect only the displayed results to be sorted (on the client) or do they expect an entirely new result set from the db, sorted accordingly?For example, if the first (default) table view displays rows A through D, should reversing the sort on that column simply display D through A, or Z through W?Or should I provide the user with the option to do either?  If so, how could I succinctly phrase the options?
Sorting displayed results vs. entire results
user experience
There's no added value to reversing data you can already see (consider the 'head' and 'tail' commands in unix). Even if you only get a snapshot of data, you still need to have access to all of it.