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.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[] 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"`
}
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.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.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
}
Here I had to convert the string slice to an interface slice.
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