Selection

occurs when the user clicks on a range slider. During selection, the algorithm computes the auxiliary data structures, which depend on the currently selected attribute and the current ranges for the other attributes. Various experiments with user interfaces show that we must respond to the mouse click in about 1 second in order not to annoy the user. At the cost of a factor of 2 in memory, we could precompute the auxiliary data structures whenever the mouse is moved close to a new range slider. Using somewhat more memory, we could steal cycles from the query operation in order to precompute the auxiliary data structures for several sliders. Thus 1 second may be an overly conservative bound on the time for selection.