code: func (t *Table) ColumnBetweenRowCount(sc *stmtctx.StatementContext, a, b types.Datum, colID int64) float64 {
  	c, ok := t.Columns[colID]
  	if !ok || c.IsInvalid(sc, t.Pseudo) {
  		return float64(t.Count) / pseudoBetweenRate
  	}
  	count := c.BetweenRowCount(a, b)
  	if a.IsNull() {
  		count += float64(c.NullCount)
  	}
  	return count * c.GetIncreaseFactor(t.Count)
  }
docs: // ColumnBetweenRowCount estimates the row count where column greater or equal to a and less than b.