When Should I Use FirstOrCreate() vs. FirstOrInit() in GORM?

Create or Update a Record with GORM

GORM offers two methods for managing records in your database: FirstOrCreate() and FirstOrInit(). However, sometimes you may encounter scenarios where you need to differentiate between creating and updating a record.

Checking for Record Creation

FirstOrCreate() attempts to find a record based on the specified criteria. If it exists, it returns the existing record. If it doesn't exist, it creates a new record and returns the newly created one.

To check if a record was actually created, you can use the Create method in a transaction. If the transaction succeeds, the record was created. If the transaction fails, it means the record already existed and was not created.

func CreateOrUpdateRecord(tx *gorm.DB, record *Model) error {
    if err := tx.Create(record).Error; err != nil {
        return err // Record already exists
    }

    return nil // Record created
}

Upsert with GORM

As of GORM 1.20.x, a convenient feature called "Upsert" is available. It combines the functionality of CreateOrUpdateRecord by providing a compatible "Upsert-On-Conflict" mechanism.

// Update columns to new value on `id` conflict
tx.Clauses(clause.OnConflict{
    Columns:   []clause.Column{{Name: "id"}}, // key column
    DoUpdates: clause.AssignmentColumns([]string{"name", "age"}), // columns needed to be updated
}).Create(&users)

This query translates into SQL statements like:

• MERGE INTO... WHEN NOT MATCHED THEN INSERT... WHEN MATCHED THEN UPDATE... (SQL Server)
• INSERT INTO... ON CONFLICT (...) DO UPDATE SET... (PostgreSQL)
• INSERT INTO... ON DUPLICATE KEY UPDATE... (MySQL)

FirstOrInit vs. FirstOrCreate

It's important to note that FirstOrInit() and FirstOrCreate() serve different purposes. FirstOrInit() initializes a struct but does not create a record in the database. FirstOrCreate(), on the other hand, will create a record and then query it into the provided struct.

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