Transaction using DBResolver (two databases)

[anshuljhawar]

Your Question

I am trying to use transaction in a sharded database. So I have two databases master and shard1.

Following code is being used to start the transaction

// tx := repo.database.Begin() // transaction to be used for master database
tx := repo.database.Clauses(dbresolver.Use("shard1"), dbresolver.Write).Begin()

But still this transaction is creating entries in the master database.

The document you expected this should be explained

https://gorm.io/docs/dbresolver.html

Expected answer

Transaction should be allowed separately for both master and shard1

Are transactions allowed only in one database? Or can we have transactions for any database, is there a different syntax/way to achieve this?

[jinzhu]

sorry, it is not supported now.

[anshuljhawar]

@jinzhu thanks! .. any plans to pick it up soon?

[SantoshSah]

@jinzhu Any update on this? Or any work around while using multiple databases and want to have transaction?

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[anshuljhawar]

@jinzhu ... Looking at the code found this piece of code in plugin -> dbresolver-> callbacks.go

func (dr *DBResolver) switchSource(db *gorm.DB) {
    if !isTransaction(db.Statement.ConnPool) {
        db.Statement.ConnPool = dr.resolve(db.Statement, Write)
    }
}

Is there any specific reason why switching source is disabled during a transaction?

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[bruce0205]

@jinzhu Any update on this? Or any work around while using multiple databases and want to have transaction?

I used dblink as my work around solution for mysql.

tx := db.Begin()
if err := tx.Table(os.Getenv("app_db1") + ".test").Create(&test1).Error; err != nil {
    tx.Rollback()
    return err
} 
if err := tx.Table(os.Getenv("app_db2") + ".test").Create(&test2).Error; err != nil {
    tx.Rollback()
    return err
}
tx.Commit()
return nil

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