code: func (h *Handle) HandleDDLEvent(t *util.Event) error {
  	switch t.Tp {
  	case model.ActionCreateTable, model.ActionTruncateTable:
  		ids := getPhysicalIDs(t.TableInfo)
  		for _, id := range ids {
  			if err := h.insertTableStats2KV(t.TableInfo, id); err != nil {
  				return err
  			}
  		}
  	case model.ActionAddColumn:
  		ids := getPhysicalIDs(t.TableInfo)
  		for _, id := range ids {
  			if err := h.insertColStats2KV(id, t.ColumnInfo); err != nil {
  				return err
  			}
  		}
  	}
  	return nil
  }
docs: // HandleDDLEvent begins to process a ddl task.