code: func (c *Column) IsInvalid(sc *stmtctx.StatementContext, collPseudo bool) bool {
  	if collPseudo && c.NotAccurate() {
  		return true
  	}
  	if c.NDV > 0 && c.Len() == 0 && sc != nil {
  		sc.SetHistogramsNotLoad()
  		HistogramNeededColumns.insert(tableColumnID{TableID: c.PhysicalID, ColumnID: c.Info.ID})
  	}
  	return c.TotalRowCount() == 0 || (c.NDV > 0 && c.Len() == 0)
  }
docs: // IsInvalid checks if this column is invalid. If this column has histogram but not loaded yet, then we mark it
  // as need histogram.