How to Ensure Error Handling During Entity Deletion in GORM when Rows are Not Found?

Error Handling during Entity Deletion in GORM

When working with a database, it's crucial to handle potential errors gracefully. In GORM, the Delete function, intended to remove an entity from the database, presents a specific issue where multiple calls with the same identifier don't trigger an error.

The Default Behavior

By default, GORM doesn't consider attempting to delete a non-existent row in the database as an error. Therefore, the Delete function simply returns nil in such cases, even if it fails to remove the entity.

Identifying the Root Cause

This behavior stems from the fact that GORM follows the SQL standard, which doesn't define deleting a non-existent row as an error. As a result, GORM doesn't inherently throw an error when you try to delete a non-existent row.

Custom Error Handling

If you need to return an error when attempting to delete a non-existent row, you have to manually check the RowsAffected field of the Delete function's result. Here's how you can modify your code:

<code class="go">func DeleteCategory(id uint) error {
    c := Category{ID: id}

    db := db.Delete(&c)
    if db.Error != nil {
        return db.Error
    } else if db.RowsAffected < 1 {
        return fmt.Errorf("row with id=%d cannot be deleted because it doesn't exist", id)
    }

    return nil
}</code>

In this modified code:

• We first check for any other errors that may have occurred during the execution of the Delete function.
• If db.Error is nil, we check the RowsAffected field. If it's less than 1, it means no row was affected, indicating that the row with the given id doesn't exist.
• In that case, we return a custom error message to indicate the failure of the operation.

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