level_handler.go
func (s *levelHandler) overlappingTables(_ levelHandlerRLocked, kr keyRange) (int, int) {
	if len(kr.left) == 0 || len(kr.right) == 0 {
		return 0, 0
	}
	left := sort.Search(len(s.tables), func(i int) bool {
		return y.CompareKeys(kr.left, s.tables[i].Biggest()) <= 0
	})
	right := sort.Search(len(s.tables), func(i int) bool {
		return y.CompareKeys(kr.right, s.tables[i].Smallest()) < 0
	})
	return left, right
}
func (s *levelHandler) overlappingTables(_ levelHandlerRLocked, kr keyRange) (int, int) {
	if len(kr.left) == 0 || len(kr.right) == 0 {
		return 0, 0
	}
	left := sort.Search(len(s.tables), func(i int) bool {
		return y.CompareKeys(kr.left, s.tables[i].Biggest()) <= 0
	})
	right := sort.Search(len(s.tables), func(i int) bool {
		return y.CompareKeys(kr.right, s.tables[i].Smallest()) < 0
	})
	return left, right
}
// overlappingTables returns the tables that intersect with key range. Returns a half-interval.
// This function should already have acquired a read lock, and this is so important the caller must
// pass an empty parameter declaring such.