为选择查询传递可变参数

Question

我正在尝试按如下方式构建查询，这里我使用的是 gorp。func GetAgregatedDownloadsFromTo(constrains Constrains) [] dao.NameValue {    dbMap := utils.GetDBConnection("radsummary");    defer dbMap.Db.Close()    var totalDailyDownloads[] NameValue    query := "SELECT SUM(outputoctets) as value ,date as name FROM dailyacct where date >= ? AND date < ? "    if len(constrains.LocationGroups) > 0 {        query = query + " AND calledstationid=? "        for i := 1; i< len(constrains.LocationGroups); i++ {            query = query + " OR calledstationid=? "        }        query = query + " group by date"        print(query)        _, err := dbMap.Select(&totalDailyDownloads, query, constrains.From, constrains.To, constrains.LocationGroups...)        if err != nil {            panic(err.Error()) // proper error handling instead of panic        }    }    return totalDailyDownloads}type Constrains struct {    From string `json:"from"`    To string   `json:"to"`    LocationGroups []string    `json:"locationgroups"`}查询构造基于 constrains.LocationGroups 的长度发生。我遇到的麻烦是将可变数量的 args 传递给 Select 查询，一旦我给出了 constrains.LocationGroups... 作为选择查询参数，它会引发编译器错误too many arguments in call to dbMap.Select有没有可能达到这种要求？。感谢您的投入。

Answer 1

找到了一个基于Pass string slice to variadic empty interface 参数的答案

以下是完成任务的更新代码

func GetAgregatedDownloadsFromTo(constrains dao.Constrains) [] dao.NameValue {

    dbMap := utils.GetDBConnection("radsummary");

    defer dbMap.Db.Close()

    var totalDailyDownloads[] dao.NameValue

    query := "SELECT SUM(outputoctets) as value ,date as name FROM dailyacct where date >= ? AND date < ? "

    if len(constrains.LocationGroups) > 0 {

        args := make([]interface{}, len(constrains.LocationGroups)+2)

        args[0] = constrains.From

        args[1] = constrains.To

        for index, value := range constrains.LocationGroups { args[index+2] = value }

        query = query + " AND calledstationid=? "

        for i := 1; i< len(constrains.LocationGroups); i++ {

            query = query + " OR calledstationid=? "

        }

        query = query + " group by date"

        print(query)

        _, err := dbMap.Select(&totalDailyDownloads, query, args...)

        if err != nil {

            panic(err.Error()) // proper error handling instead of panic

        }

    }

    return totalDailyDownloads

}

在这里，我不得不将字符串切片转换为接口切片。