Django的inspectdb不會執行ManyToManyField

Question

所以我只測試了一件事情，製作下列表格。

# Dump of table driverclass 
# ------------------------------------------------------------ 

CREATE TABLE `driverclass` (
    `id` int(11) unsigned NOT NULL AUTO_INCREMENT, 
    `name` varchar(20) DEFAULT NULL, 
    PRIMARY KEY (`id`) 
) ENGINE=InnoDB DEFAULT CHARSET=latin1; 

# Dump of table event 
# ------------------------------------------------------------ 

CREATE TABLE `event` (
    `id` int(11) unsigned NOT NULL AUTO_INCREMENT, 
    `name` varchar(20) DEFAULT NULL, 
    PRIMARY KEY (`id`) 
) ENGINE=InnoDB DEFAULT CHARSET=latin1; 

# Dump of table driver 
# ------------------------------------------------------------ 

CREATE TABLE `driver` (
    `id` int(11) unsigned NOT NULL AUTO_INCREMENT, 
    `name` varchar(20) DEFAULT NULL, 
    PRIMARY KEY (`id`) 
) ENGINE=InnoDB DEFAULT CHARSET=latin1; 

# Dump of table driver_driverclass_event 
# ------------------------------------------------------------ 

CREATE TABLE `driver_driverclass_event` (
    `id` int(11) unsigned NOT NULL AUTO_INCREMENT, 
    `driver_id` int(11) unsigned DEFAULT NULL, 
    `event_class_id` int(11) unsigned DEFAULT NULL, 
    PRIMARY KEY (`id`), 
    KEY `driver_id` (`driver_id`), 
    KEY `event_class_id` (`event_class_id`), 
    CONSTRAINT `driver_driverclass_event_ibfk_2` FOREIGN KEY (`event_class_id`) REFERENCES `driverclass_event` (`id`), 
    CONSTRAINT `driver_driverclass_event_ibfk_1` FOREIGN KEY (`driver_id`) REFERENCES `driver` (`id`) 
) ENGINE=InnoDB DEFAULT CHARSET=latin1; 

# Dump of table driverclass_event 
# ------------------------------------------------------------ 

CREATE TABLE `driverclass_event` (
    `id` int(11) unsigned NOT NULL AUTO_INCREMENT, 
    `event_id` int(11) unsigned DEFAULT NULL, 
    `driverclass_id` int(11) unsigned DEFAULT NULL, 
    PRIMARY KEY (`id`), 
    KEY `event_id` (`event_id`), 
    KEY `driverclass_id` (`driverclass_id`), 
    CONSTRAINT `driverclass_event_ibfk_2` FOREIGN KEY (`driverclass_id`) REFERENCES `driverclass` (`id`), 
    CONSTRAINT `driverclass_event_ibfk_1` FOREIGN KEY (`event_id`) REFERENCES `event` (`id`) 
) ENGINE=InnoDB DEFAULT CHARSET=latin1; 

這應該是ManyToManyField的關係。然而，Djangosinspectdb將它看作是具有大量ForeignKeys的5個模型。請問Djangosinspectdb是否考慮了ManyToManyFields，還是我的databasemodel錯誤？

Answer 1

您的數據庫模式看起來沒問題。但是，Django不會像您發現的那樣自動創建「多對多」字段。 driverclass_事件和** driver_driverclass_event **的模型是所謂的「通過」模型。通常情況下，還要定義ManyToManyField在關係的兩端「到」模型指定正確的：

class Event(db.Model): 
    pass 

class DriverClass(db.Model): 
    events = db.ManyToManyField(Event, through='DriverClassEvent') 

class DriverClassEvent(db.Model): 
    driver_class = db.ForeignKeyField(DriverClass) 
    event = db.ForeignKeyField(Event) 

參見：https://docs.djangoproject.com/en/dev/topics/db/models/#extra-fields-on-many-to-many-relationships

通常通過當你想存儲信息車型均採用約爲的關係，如關係的開始日期或使用外鍵引用此關係。在您的示例中，您存儲哪些驅動程序與DriverClassEvent有關係。所以DriverClassEvent應該有一個模型來引用它。

class DriverDriverClassEvent(db.Model): 
    driver = db.ForeignKeyField(Driver) 
    driver_class_event = db.ForeignKeyField(DriverClassEvent) 

class Driver(db.Model): 
    driver_class_events = db.ManyToManyField(DriverClassEvent, through='DriverDriverClassEvent') 

現在你可以放下DriverDriverClassEvent，你不要將任何數據存儲有關的關係，或參考其他車型的關係。所以，最後一個例子變成*：

class Driver(db.Model): 
    driver_class_events = db.ManyToManyField(DriverClassEvent, db_table='driver_driverclass_event') 

*請注意，您不必在字段名控制，所以那些不得不匹配Django的自動生成的字段名。