code: func (t *Table) Copy() *Table {
  	newHistColl := HistColl{
  		PhysicalID:     t.PhysicalID,
  		HavePhysicalID: t.HavePhysicalID,
  		Count:          t.Count,
  		Columns:        make(map[int64]*Column),
  		Indices:        make(map[int64]*Index),
  		Pseudo:         t.Pseudo,
  		ModifyCount:    t.ModifyCount,
  	}
  	for id, col := range t.Columns {
  		newHistColl.Columns[id] = col
  	}
  	for id, idx := range t.Indices {
  		newHistColl.Indices[id] = idx
  	}
  	nt := &Table{
  		HistColl: newHistColl,
  		Version:  t.Version,
  		Name:     t.Name,
  	}
  	return nt
  }
docs: // Copy copies the current table.