Пример #1
0
func (this *DNF) VisitLike(expr *expression.Like) (interface{}, error) {
	err := expr.MapChildren(this)
	if err != nil {
		return nil, err
	}

	re := expr.Regexp()
	if re == nil {
		return expr, nil
	}

	prefix, complete := re.LiteralPrefix()
	if complete {
		eq := expression.NewEq(expr.First(), expression.NewConstant(prefix))
		return eq, nil
	}

	if prefix == "" {
		return expr, nil
	}

	var and expression.Expression
	le := expression.NewLE(expression.NewConstant(prefix), expr.First())
	last := len(prefix) - 1
	if prefix[last] < math.MaxUint8 {
		bytes := []byte(prefix)
		bytes[last]++
		and = expression.NewAnd(le, expression.NewLT(
			expr.First(),
			expression.NewConstant(string(bytes))))
	} else {
		and = expression.NewAnd(le, expression.NewLT(
			expr.First(),
			expression.EMPTY_ARRAY_EXPR))
	}

	return and, nil
}