defer：在长时间运行的功能中使用？

Question

Here is a sample function that takes a connection to the database from the connection pool and does a query and processes the result returned.

func dbQuery() error {
    con := db.getConn()
    result, err := con.Query()
    if err != nil {
       return err
    }
    defer con.close() // or con.close()
    // Processing the result takes a long time


    return nil
}

Processing the result in this case takes a long time and close is not called for the connection, which means it is not returned to the connection pool.
Is it ok to directly call con.close() in cases like this when we know the resources are held for a long time even when they are not needed?

Answer 1

My suggestion would be to refactor your code. This way a defer closes the connection before you process the result:

func dbQuery() error {
    result, err := getResult()
    if err != nil {
        return err
    }
    // Processing the result takes a long time

    return nil
}

func getResult() (*Rows, error) {
    con := db.getConn()
    defer con.close() // or con.close()

    result, err := con.Query()
    if err != nil {
        return nil, err
    }

    return result, err
}