How to pass in variable length variable to statement.Exec? - go

Question

For example
func Query(myvarlist []string) {
stmt, err := tx.Prepare("SELECT * FROM mytable WHERE
myvar = $1 AND myvar2 = $2".......)
defer stmt.Close()
if _, err := stmt.Exec(myvarlist....); err != nil {
}
Can we pass in Exec a variable length variable?

Answer 1

You can do something like the this:
func Query() {
db, err := sql.Open("pgx", `postgresql://CONNSTRING`)
if err != nil {
panic(err)
}
queryParamMap := map[string]string{
"id": "6",
"name": "1",
}
// Build up statement and params
cols := make([]string, len(queryParamMap))
args := make([]any, len(queryParamMap))
i := 0
for k, v := range queryParamMap {
cols[i] = fmt.Sprintf("%s = $%d", k, i+1) // WARNING - SQL Injection possible here if col names are not sanitised
args[i] = v
i++
}
// Using Prepare because the question used it but this is only worthwhile if you will run stmt multiple times
stmt, err := db.Prepare(`SELECT id FROM devices WHERE ` + strings.Join(cols, " and "))
if err != nil {
panic(err)
}
defer stmt.Close()
rows, err := stmt.Query(args...)
if err != nil {
panic(err)
}
defer rows.Close()
for rows.Next() {
var id int
if err = rows.Scan(&id); err != nil {
panic(err)
}
fmt.Println("value:", id)
}
// Should check rows.Error() etc but this is just an example...
}
I've put the column names and values into a map because it was not clear where any extra column names would come from in your question but hopefully this provides the info you need.
This example is also using Query rather than Exec (because it's easier to test) but the same approach will work with Exec.
Note: Take a look at squirrel for an example of how to take this a lot further....