MariaDB better support

[celogeek]

Describe the feature

MariaDB support more feature than MySQL (old version at least).

The one I would love to have is the support of RETURNING clause on the Create operation.

I see a detection of MariaDB, so why not allow additional features there?

I'm trying to create or get a row while inserting. The goal is to handle properly concurrent insert than try to create the same data.

So What I do is something like:

	if err = s.DB.Transaction(func(tx *gorm.DB) (err error) {
		if err = tx.Clauses(clause.OnConflict{DoNothing: true}).Create(u).Error; err != nil {
			return
		}

		if u.ID == 0 {
			if err = tx.First(u, "sha1 = ?", u.Sha1).Error; err != nil {
				return
			}
		}

Motivation

I've got 3 tables to update. I need the ID of the first one to create the entry in the over tables. And 2 parallel request can run the same code. I don't want to end up with a duplicate error.

The create SQL should be:

INSERT INTO T (C1, C2) VALUES(V2, V2) ON DUPLICATE KEY UPDATE id=id RETURNING *

Or ID by default. That could be overwritten.

[celogeek]

I endup using Raw mode:

func (u *URL) Create(tx *gorm.DB) error {
	return tx.Raw(`
	INSERT INTO urls (
		url,
		sha1,
		created_at
	) VALUES(
		?,
		?,
		NOW()
	) ON DUPLICATE KEY UPDATE id=id
	RETURNING *
	`, &u.Url, u.CheckSumURL()).Scan(u).Error
}

May be I can build the SQL with the clause builder instead and add the RETURNING * on the SQL.