code: func (ir *IndexRange) IsPoint(sc *variable.StatementContext) bool {
  	if len(ir.LowVal) != len(ir.HighVal) {
  		return false
  	}
  	for i := range ir.LowVal {
  		a := ir.LowVal[i]
  		b := ir.HighVal[i]
  		if a.Kind() == types.KindMinNotNull || b.Kind() == types.KindMaxValue {
  			return false
  		}
  		cmp, err := a.CompareDatum(sc, b)
  		if err != nil {
  			return false
  		}
  		if cmp != 0 {
  			return false
  		}
  	}
  	return !ir.LowExclude && !ir.HighExclude
  }
docs: // IsPoint returns if the index range is a point.