Phantom read allows duplicate email

Code reviewDatabases & SQLSenior–Staff~28 min

Review this Go signup function that enforces one account per email.

What a strong answer looks like

Separate real bugs from style. Rank issues by severity, point at the root cause rather than the symptom, and suggest a concrete fix, specific and kind.

0:00 of about 28 min

Mark a line and say what kind of problem it is.0 findings

1func CreateUser(ctx context.Context, db *sql.DB, email, name string) error {

2 tx, _ := db.BeginTx(ctx, &sql.TxOptions{Isolation: sql.LevelReadCommitted})

3 var n int

4 tx.QueryRowContext(ctx,

5 "SELECT COUNT(*) FROM users WHERE email = $1", email).Scan(&n)

6 if n > 0 {

7 tx.Rollback()

8 return ErrEmailTaken

9 }

10 _, err := tx.ExecContext(ctx,

11 "INSERT INTO users (email, name) VALUES ($1, $2)", email, name)

12 if err != nil {

13 tx.Rollback()

14 return err

15 }

16 return tx.Commit()

17}

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