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

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

	if level < 0 {
		level = s.version_NB().pickLevel(t.min.ukey(), t.max.ukey())
	}
	c.rec.addTableFile(level, t)

	s.logf("[email protected] created L%[email protected]%d N·%d S·%s %q:%q", level, t.file.Num(), n, shortenb(int(t.size)), t.min, t.max)

	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))
}

func (d *DB) recoverJournal() error {
	s := d.s
	icmp := s.cmp

	ff0, err := s.getFiles(storage.TypeJournal)
	if err != nil {
		return err
	}
	ff1 := files(ff0)
	ff1.sort()
	ff2 := make([]storage.File, 0, len(ff1))
	for _, file := range ff1 {
		if file.Num() >= s.stJournalNum || file.Num() == s.stPrevJournalNum {
			s.markFileNum(file.Num())
			ff2 = append(ff2, file)
		}
	}

	var jr *journal.Reader
	var of storage.File
	var mem *memdb.DB
	batch := new(Batch)
	cm := newCMem(s)
	buf := new(util.Buffer)
	// Options.
	strict := s.o.GetStrict(opt.StrictJournal)
	checksum := s.o.GetStrict(opt.StrictJournalChecksum)
	writeBuffer := s.o.GetWriteBuffer()
	recoverJournal := func(file storage.File) error {
		s.logf("[email protected] recovering @%d", file.Num())
		reader, err := file.Open()
		if err != nil {
			return err
		}
		defer reader.Close()
		if jr == nil {
			jr = journal.NewReader(reader, dropper{s, file}, strict, checksum)
		} else {
			jr.Reset(reader, dropper{s, file}, strict, checksum)
		}
		if of != nil {
			if mem.Len() > 0 {
				if err := cm.flush(mem, 0); err != nil {
					return err
				}
			}
			if err := cm.commit(file.Num(), d.seq); err != nil {
				return err
			}
			cm.reset()
			of.Remove()
			of = nil
		}
		// Reset memdb.
		mem.Reset()
		for {
			r, err := jr.Next()
			if err != nil {
				if err == io.EOF {
					break
				}
				return err
			}
			buf.Reset()
			if _, err := buf.ReadFrom(r); err != nil {
				if strict {
					return err
				}
				continue
			}
			if err := batch.decode(buf.Bytes()); err != nil {
				return err
			}
			if err := batch.memReplay(mem); err != nil {
				return err
			}
			d.seq = batch.seq + uint64(batch.len())
			if mem.Size() >= writeBuffer {
				// Large enough, flush it.
				if err := cm.flush(mem, 0); err != nil {
					return err
				}
				// Reset memdb.
				mem.Reset()
			}
		}
		of = file
		return nil
	}
	// Recover all journals.
	if len(ff2) > 0 {
		s.logf("[email protected] F·%d", len(ff2))
		mem = memdb.New(icmp, toPercent(writeBuffer, kWriteBufferPercent))
		for _, file := range ff2 {
			if err := recoverJournal(file); err != nil {
				return err
			}
		}
		// Flush the last journal.
		if mem.Len() > 0 {
//.........这里部分代码省略.........

func (b *Batch) revertMemReplay(to *memdb.DB) error {
	return b.decodeRec(func(i int, t vType, key, value []byte) {
		ikey := newIKey(key, b.seq+uint64(i), t)
		to.Delete(ikey)
	})
}