英文:
Passing a variadic parameter for select query
问题
我正在尝试构建以下查询，这里我使用了gorp。
func GetAgregatedDownloadsFromTo(constrains Constrains) []dao.NameValue {dbMap := utils.GetDBConnection("radsummary")defer dbMap.Db.Close()var totalDailyDownloads []dao.NameValuequery := "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"`}
查询的构建基于constrains.LocationGroups的长度。我遇到的问题是在将可变数量的参数传递给Select查询时，一旦我将constrains.LocationGroups...作为查询参数，它就会抛出编译器错误too many arguments in call to dbMap.Select。
是否可能实现这种需求？感谢您的建议。
英文:
I'm trying to build a query as follows, here I'm using gorp.
func GetAgregatedDownloadsFromTo(constrains Constrains) [] dao.NameValue {dbMap := utils.GetDBConnection("radsummary");defer dbMap.Db.Close()var totalDailyDownloads[] NameValuequery := "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"`}
Query construction happens based on the length of constrains.LocationGroups. Trouble I'm having is passing the variable number of args to the Select query once I give constrains.LocationGroups... as select query parameters it throws a compiler error too many arguments in call to dbMap.Select
Is it possible to achieve this kind of requirement?. Appreciate your input.
答案1
得分: 0
根据https://stackoverflow.com/questions/7975095/pass-string-slice-to-variadic-empty-interface-parameter?rq=1找到了一个答案。
以下是实现该任务的更新代码：
func GetAgregatedDownloadsFromTo(constrains dao.Constrains) []dao.NameValue {dbMap := utils.GetDBConnection("radsummary")defer dbMap.Db.Close()var totalDailyDownloads []dao.NameValuequery := "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.Fromargs[1] = constrains.Tofor 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，我需要将字符串切片转换为接口切片。
英文:
Found an answer based on https://stackoverflow.com/questions/7975095/pass-string-slice-to-variadic-empty-interface-parameter?rq=1
Below is the updated code to achieve the task
func GetAgregatedDownloadsFromTo(constrains dao.Constrains) [] dao.NameValue {dbMap := utils.GetDBConnection("radsummary");defer dbMap.Db.Close()var totalDailyDownloads[] dao.NameValuequery := "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.Fromargs[1] = constrains.Tofor 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}
Here I had to convert the string slice to an interface slice.
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