Golang

From a performance perspective, what common rules should be applied to such a database schema?

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What to do if we have added all the necessary indexes, but the database still cannot handle the load and slows down?

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Why do Go developers not guarantee the order of map traversal during range?

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// GetUsersList returns a list of users. (approximately 1 million users are stored in the database) // Used to display the list of users in the admin panel. If isActive = true, only active users are returned. func (u *UsersRepo) GetUsersList(ctx context.Context, isActive bool) ([]User, error) { rows, err := u.DB.Query("SELECT id, name, phone FROM users WHERE is_active = ?", isActive) if err != nil { return nil, errors.New("error fetching user list") } var users []User // Fill in user information. for rows.Next() { var user User err := rows.Scan(&user.ID, &user.Name, &user.Phone) if err != nil { return nil, err } // Get the user's email list err, err := u.DB.QueryContext(ctx, "SELECT email FROM user_emails WHERE user_id = ?", user.ID) if err != nil { return nil, errors.New("error fetching user emails") } var emails []string for er.Next() { var email string err := rows.Scan(&email) if err != nil { return nil, err } emails = append(emails, email) } if len(emails) != 0 { for i, e := range emails { emails[i] = strings.ToLower(e) } } user.Emails = emails // Get profile information from VK API profile, err := getUserProfileFromVkApiByUserPhone(user.Phone) if err != nil { return nil, errors.New("error fetching user profile") } user.Profile = profile users = append(users, user) } if err = rows.Err(); err != nil { return nil, errors.New("error fetching user list") } }

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-- list books sorted by id, -- but swap lines 2 and 3 in the output: -- 1 Master and Margarita 100 -- 3 The Golden Calf 50 -- 2 The Twelve Chairs 200 -- 4 Eugene Onegin 250 -- 5 Belya's Stories 90 -- 6 The Three Musketeers 60

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