// Preserve older credential if we do not have
		// root credentials set via environment variable.
		globalActiveCred = cfg.Credential
	}

	// Init compression config. For future migration, Compression config needs to be copied over from previous version.
	switch cfg.Version {
	case "29":
		// V29 -> V30
		cfg.Compression.Enabled = false

Here we create the tables on an application startup event.

For production you would probably use a migration script that runs before you start your app. 🤓

/// tip

SQLModel will have migration utilities wrapping Alembic, but for now, you can use <a href="https://alembic.sqlalchemy.org/en/latest/" class="external-link" target="_blank">Alembic</a> directly.

///

		gorm.Model
		Name string
	}

	if err := DB.Migrator().RenameTable(&TableStruct{}, &NewTableStruct{}); err != nil {
		t.Fatalf("Failed to rename table, got error %v", err)
	}

	if !DB.Migrator().HasTable("new_table_structs") {
		t.Fatal("should found renamed table")
	}

	DB.Migrator().DropTable("new_table_structs")

	if DB.Migrator().HasTable(&NewTableStruct{}) {

		t.Fatalf("expected value false, got %t", ok)
	}

	formats[2].Erasure.This = ""
	if ok := formatErasureV3ThisEmpty(formats); !ok {
		t.Fatalf("expected value true, got %t", ok)
	}
}

// Tests xl format migration.
func TestFormatErasureMigrate(t *testing.T) {
	// Get test root.
	rootPath := t.TempDir()

	m := &formatErasureV1{}
	m.Format = formatBackendErasure
	m.Version = formatMetaVersionV1

	NewValuePool           FieldNewValuePool

	// In some db (e.g. MySQL), Unique and UniqueIndex are indistinguishable.
	// When a column has a (not Mul) UniqueIndex, Migrator always reports its gorm.ColumnType is Unique.
	// It causes field unnecessarily migration.
	// Therefore, we need to record the UniqueIndex on this column (exclude Mul UniqueIndex) for MigrateColumnUnique.
	UniqueIndex string
}

	if err := json.Unmarshal(b, format); err != nil {
		return "", err
	}
	return format.Erasure.Version, nil
}

// Migrates all previous versions to latest version of `format.json`,
// this code calls migration in sequence, such as V1 is migrated to V2
// first before it V2 migrates to V3.n
func formatErasureMigrate(export string) ([]byte, fs.FileInfo, error) {
	formatPath := pathJoin(export, minioMetaBucket, formatConfigFile)

   *
   * <p><b>Warning:</b> as with all function types in this package, avoid depending on the specific
   * {@code equals}, {@code hashCode} or {@code toString} behavior of the returned function. A
   * future migration to {@code java.util.function} will not preserve this behavior.
   *
   * <p>As discussed above, prefer to use the method reference {@code Object::toString} instead,

Of course, there are some cases where there's no problem in running the previous steps multiple times, in that case, it's a lot easier to handle.

/// tip

    return from(Arrays.asList(elements));
  }

  /**
   * Construct a fluent iterable from another fluent iterable. This is obviously never necessary,
   * but is intended to help call out cases where one migration from {@code Iterable} to {@code
   * FluentIterable} has obviated the need to explicitly convert to a {@code FluentIterable}.
   *
   * @deprecated instances of {@code FluentIterable} don't need to be converted to {@code

    return from(Arrays.asList(elements));
  }

  /**
   * Construct a fluent iterable from another fluent iterable. This is obviously never necessary,
   * but is intended to help call out cases where one migration from {@code Iterable} to {@code
   * FluentIterable} has obviated the need to explicitly convert to a {@code FluentIterable}.
   *
   * @deprecated instances of {@code FluentIterable} don't need to be converted to {@code