func (c *cMem) flush(mem *memdb.DB, level int) error {
	s := c.s

	// Write memdb to table.
	iter := mem.NewIterator(nil)
	defer iter.Release()
	t, n, err := s.tops.createFrom(iter)
	if err != nil {
		return err
	}

	// Pick level.
	if level < 0 {
		level = s.version_NB().pickLevel(t.imin.ukey(), t.imax.ukey())
	}
	c.rec.addTableFile(level, t)

	s.logf("mem@flush created L%d@%d N·%d S·%s %q:%q", level, t.file.Num(), n, shortenb(int(t.size)), t.imin, t.imax)

	c.level = level
	return nil
}
func isMemOverlaps(icmp *iComparer, mem *memdb.DB, min, max []byte) bool {
	iter := mem.NewIterator(nil)
	defer iter.Release()
	return (max == nil || (iter.First() && icmp.uCompare(max, iKey(iter.Key()).ukey()) >= 0)) &&
		(min == nil || (iter.Last() && icmp.uCompare(min, iKey(iter.Key()).ukey()) <= 0))
}