Transactions within a transaction

[denggj28]

I recently had the need to transaction at a point that happened to be inside another transaction. All my tests seem to indicate this is working out fine, but I can't find any documentation on this usage.

err := db.RunInTx(ctx, &sql.Options{}, func(tx bun.Tx) error {
    // below lines in another library, like call a function, use the same db connection
    subErr := db.RunInTx(ctx, &sql.Options{}, func(tx bun.Tx) error {
        // do something
    }
    // end

    if subErr != nil {
        return subErr
    }

    // do someing in this transaction
    txErr := tx.NewUpdate().Model(&m).WherePK().Exec(ctx)
    if txErr != nil {
        return txErr
    }

    return nil
}

I want to be sure - are transactions within a transaction valid in mysql or postgresql?

[hhuseyinpay]

No, it's not. For nested transactions in MySQL and PostgreSQL, you should use savepoints. But RunInTx does not utilize savepoint. You can refer to source

[slava-nikulin]

@denggj28 nested transactions are already implemented via savepoint. You don't need another library. So, you can just begin pseudo-nested transaction in RunInTx see https://github.com/uptrace/bun/blob/d2e0ef06e225732ec68372771b77161aad8144d5/db.go#L602