php - Doctrine 和 MySQL 多对多清除子

Question

我对多对多关系有一些严重的问题。在我的场景中， aCandidate可以连接很多Projects并且Project可能有很多Candidates.

CREATE TABLE `CANDIDATE` (    
  `ID` INT NOT NULL AUTO_INCREMENT ,     
  PRIMARY KEY (`ID`) )ENGINE = InnoDB;

CREATE `PROJECT` (
  `ID` INT NOT NULL AUTO_INCREMENT ,
  PRIMARY KEY (`ID`)ENGINE = InnoDB;

CREATE TABLE `PROJECT_CANDIDATE` (
  `CANDIDATE_ID` INT NULL ,
  `PROJECT_ID` INT NULL ,

  CONSTRAINT `FK_PROJECT_CANDIDATE`
    FOREIGN KEY (`CANDIDATE_ID` )
    REFERENCES `CANDIDATE` (`ID` )
    ON DELETE NO ACTION
    ON UPDATE NO ACTION)

  CONSTRAINT `FK_CANDIDATE_PROJECT`
    FOREIGN KEY (`PROJECT_ID` )
    REFERENCES `PROJECT` (`ID` )
    ON DELETE NO ACTION
    ON UPDATE NO ACTION)ENGINE = InnoDB;

教义映射如下所示：

class Project
{
    //.... other fields

    /**
     * @var \Doctrine\Common\Collections\Collection
     *
     * @ORM\ManyToMany(targetEntity="Candidate", mappedBy="projects", fetch="LAZY",cascade={"persist","merge"},orphanRemoval=true)
     */
    private $candidates;
}



class Candidate
{
        //.... other fields
    /**
     * @var \Doctrine\Common\Collections\Collection
     *
     * @ORM\ManyToMany(targetEntity="Project", inversedBy="candidates", fetch="LAZY",cascade={"persist","merge"},orphanRemoval=true)
     * @ORM\JoinTable(name="project_candidate",
     *   joinColumns={
     * @ORM\JoinColumn(name="CANDIDATE_ID", referencedColumnName="ID")
     *   },
     *   inverseJoinColumns={
     * @ORM\JoinColumn(name="PROJECT_ID", referencedColumnName="ID")
     *   }
     * )
     */
    private $projects;
}

我的问题是，为什么从这样的项目中删除候选人时：

 //get $project with EntityManager
 $project->candidates->clear();

表中的条目Candidates也被删除，即使我有ON UPDATE/DELETE NO ACTION' for FK inPROJECT_CANDIDATE`？

Answer 1

我相信这是因为orphanRemoval=trueManyToMany 注释声明中的选项。

请参阅 Doctrine 2 文档的适当部分。