}

// MigrateColumn migrate column
func (m Migrator) MigrateColumn(value interface{}, field *schema.Field, columnType gorm.ColumnType) error {
	if field.IgnoreMigration {
		return nil
	}

	// found, smart migrate
	fullDataType := strings.TrimSpace(strings.ToLower(m.DB.Migrator().FullDataTypeOf(field).SQL))
	realDataType := strings.ToLower(columnType.DatabaseTypeName())

	var (
		alterColumn bool

	tx := db.Begin()
	defer func() {
		if r := recover(); r != nil {
			tx.Rollback()
		}
	}()
	if err := tx.Error; err != nil {
		t.Errorf("Failed to start transaction, got error %v\n", err)
	}

	if err := tx.Where("name=?", "zzjin").Delete(&User{}).Error; err != nil {
		tx.Rollback()
		t.Errorf("Failed to run one transaction, got error %v\n", err)
	}

		sql = numericPlaceholder.ReplaceAllString(sql, "$$$1$$")

		sql = numericPlaceholderRe.ReplaceAllStringFunc(sql, func(v string) string {
			num := v[1 : len(v)-1]
			n, _ := strconv.Atoi(num)

			// position var start from 1 ($1, $2)
			n -= 1
			if n >= 0 && n <= len(vars)-1 {
				return vars[n]
			}
			return v
		})
	}

	return sql

		return
	}

	conn, err := sqlDB.Conn(tx.Statement.Context)
	if err != nil {
		return
	}

	defer conn.Close()
	tx.Statement.ConnPool = conn
	return fc(tx)
}

// Transaction start a transaction as a block, return error will rollback, otherwise to commit. Transaction executes an
// arbitrary number of commands in fc within a transaction. On success the changes are committed; if an error occurs

	}

	return tx
}

// WithContext change current instance db's context to ctx
func (db *DB) WithContext(ctx context.Context) *DB {
	return db.Session(&Session{Context: ctx})
}

// Debug start debug mode
func (db *DB) Debug() (tx *DB) {
	tx = db.getInstance()
	return tx.Session(&Session{
		Logger: db.Logger.LogMode(logger.Info),
	})
}