BitmapFactory bitmapFactory = index.getBitmapFactoryForDimensions();
final ImmutableBitmap baseFilter;
if (filter == null) {
baseFilter = bitmapFactory.complement(bitmapFactory.makeEmptyImmutableBitmap(), index.getNumRows());
} else {
ColumnSelectorBitmapIndexSelector selector = new ColumnSelectorBitmapIndexSelector(bitmapFactory, index);
baseFilter = filter.getBitmapIndex(selector);
}