doctrine - Doctrine 2 何时会在使用复合键时出错？

Question

我最近正在阅读Doctrine 2's best practices并被此阻止:

25.3. Avoid composite keys
Even though Doctrine fully supports composite keys it is best not to use them if possible. Composite keys require additional work by Doctrine and thus have a higher probability of errors.

我不明白的是:如果“Doctrine完全支持复合键”，那么在处理此类键时怎么会出错？

因此，我想以社区 wiki 的身份提出这个问题，希望它能帮助我们理解“错误概率” 是什么:

您是否有示例可以分享，以展示您遇到的 Doctrine 2 未能很好地/按其应有的方式处理复合键的情况？

Answer 1

就我而言，我相信我已经遇到了一个非常基本的数据库模式的一些问题，该模式包含一个主键由 2 个外键组成的表:

当我生成模型时，不会创建与 product_i18n 实体对应的实体:

$ php doctrine-module.php orm:convert-mapping --namespace="Dbi\Entity\\" \
--from-database --force annotation module/Dbi/src/
Processing entity "Dbi\Entity\Locale"
Processing entity "Dbi\Entity\Product"

$ php doctrine-module.php orm:generate-entities --generate-annotations=1 \
module/Dbi/src
Processing entity "Dbi\Entity\Locale"
Processing entity "Dbi\Entity\Product"

但是，我相信我的database schema已正确创建:

  PRIMARY KEY (`product_id`, `locale_id`) ,
  INDEX `fk_product_i18n_locale` (`locale_id` ASC) ,
  INDEX `fk_product_i18n_product` (`product_id` ASC) ,
  CONSTRAINT `fk_product_i18n_locale`
    FOREIGN KEY (`locale_id` )
    REFERENCES `mydb`.`locale` (`id` ),
  CONSTRAINT `fk_product_i18n_product`
    FOREIGN KEY (`product_id` )
    REFERENCES `mydb`.`product` (`id` )

此外，Doctrine 2 的 Schema Manager 显示 Doctrine 似乎完美地理解了这种关系(var_dump 输出被更改以使其更加简洁) :删除诸如 array、RECURSION、string...):

$em = $this->getServiceLocator()->get('doctrine.entitymanager.orm_default');
$sm = $em->getConnection()->getSchemaManager();
var_dump($sm->->listTables());

object(Doctrine\DBAL\Schema\Table)#290 (10) {
["_name":protected]=> "product_i18n"

["_indexes":protected]=>
  ["primary"]=>
    ["_columns":protected]=>
      [0]=> "product_id"
      [1]=> "locale_id"

["_fkConstraints":protected]=>
  ["fk_product_i18n_locale"]=>
  object(Doctrine\DBAL\Schema\ForeignKeyConstraint)#285 (9) {
    ["_localColumnNames":protected]=> "locale_id"
    ["_foreignTableName":protected]=> "locale"
    ["_foreignColumnNames":protected]=> "id"

  ["fk_product_i18n_product"]=>
  object(Doctrine\DBAL\Schema\ForeignKeyConstraint)#286 (9) {
    ["_localColumnNames":protected]=> "product_id"
    ["_foreignTableName":protected]=> "product"
    ["_foreignColumnNames":protected]=> "id"

因此，我所处的情况是，我可以查询 product_i18n 表的架构，但无法与该表交互，因为未生成相应的实体模型。

更新:正如user1136666指出的:known issues and limitations page颂歌陈述如下:

Although we state that we support composite primary keys that does not currently include foreign keys as primary key columns.

解决方法是定义代理键并在外键上添加唯一约束，如下所示:

CREATE  TABLE IF NOT EXISTS `mydb`.`product_i18n` (
  `id` INT NOT NULL AUTO_INCREMENT ,
  `name` VARCHAR(45) NULL ,
  `description` TEXT NULL ,
  `created_at` DATETIME NULL ,
  `modified_at` DATETIME NULL ,
  `product_id` INT NOT NULL ,
  `locale_id` INT NOT NULL ,
  INDEX `fk_product_i18n_locale` (`locale_id` ASC) ,
  INDEX `fk_product_i18n_product` (`product_id` ASC) ,
  PRIMARY KEY (`id`) ,
  UNIQUE (`locale_id` , `product_id`),
  CONSTRAINT `fk_product_i18n_locale`
    FOREIGN KEY (`locale_id` )
    REFERENCES `mydb`.`locale` (`id` )
  CONSTRAINT `fk_product_i18n_product`
    FOREIGN KEY (`product_id` )
    REFERENCES `mydb`.`product` (`id` )
ENGINE = InnoDB;

功能请求:http://www.doctrine-project.org/jira/browse/DDC-1926