Kotlin使用Room数据库报Foreign Key constraint failed错误排查

已多角度排查相关代码、检索对应解决方案，了解到有说法称Room的自增主键字段不可作为外键关联的父列，但此前在Java语言中已成功实现同类逻辑，目前学习Kotlin开发时复现该逻辑却运行异常。

实体类定义 #

User实体 #

@Entity
@Parcelize
data class User(
    @PrimaryKey(autoGenerate = true) val id: Long,
    val email: String,
    val name: String,
    val defaultRecipient: String
) : Parcelable

University实体 #

@Parcelize
@Entity(
    foreignKeys = [ForeignKey(
        entity = User::class,
        parentColumns = ["id"],
        childColumns = ["userId"],
        onDelete = ForeignKey.CASCADE,
        onUpdate = ForeignKey.CASCADE
    )], indices = [Index(value = ["userId"])]
)
data class University(
    val userId: Long,
    @PrimaryKey @NonNull val name: String
) : Parcelable {
    override fun equals(other: Any?): Boolean {
        if(other !is University) return false
        return (this.name == other.name) && this.userId == other.userId
    }

    override fun toString(): String {
        return this.name
    }
}

Semester实体 #

@Parcelize
@Entity(
    foreignKeys = [ForeignKey(
        entity = University::class,
        parentColumns = ["name"],
        childColumns = ["universityName"],
        onDelete = ForeignKey.CASCADE,
        onUpdate = ForeignKey.CASCADE
    )], indices = [Index(value = ["universityName"])]
)
data class Semester(
    val title: String,
    val universityName: String,
    @PrimaryKey(autoGenerate = true) val id: Long
) : Parcelable

Course实体 #

@Parcelize
@Entity(
    foreignKeys = [ForeignKey(
        entity = Semester::class,
        parentColumns = ["id"],
        childColumns = ["semesterId"],
        onDelete = ForeignKey.CASCADE,
        onUpdate = ForeignKey.CASCADE
    )], indices = [Index(value = ["semesterId"])]
)
data class Course(
    val title: String,
    val code: String,
    val semesterId: Long,
    @PrimaryKey(autoGenerate = true) val id: Long
) : Parcelable

异常触发代码 #

执行以下数据插入逻辑时，系统抛出外键约束错误：

val user = userDao.getUser()
userDao.insertUniversity(University(user.id, "Chuckles University"))
val university = userDao.getUniversitiesByUser(user.id)[0]
userDao.insertSemester(Semester("Fall 22", "Comsats Wah", 0))
val semester = userDao.getSemestersByUniversity(university.name)[0]
userDao.insertCourse(Course("Introduction to Programming", "CSC100", semester.id, 0))

• 「Room自增主键字段不可作为外键关联父列」的说法不成立，之前Java版本能正常运行就是直接证明，本次报错和自增主键特性无关。
• 核心错误是插入Semester时外键字段传值不匹配：刚插入的University记录名称为Chuckles University，但构造Semester对象时传入的关联学校名称是"Comsats Wah"，数据库中不存在对应name值的University记录，外键约束校验直接失败抛出异常，代码根本不会执行到后续查询学期、插入课程的步骤。
• 存在一处潜在隐患：当前构造Semester、Course等带自增主键的实体时，手动给id字段传0作为初始值，虽然Room默认会将自增主键传入的0识别为「需要自动生成ID」，但更稳妥的写法是给实体类的自增id字段设置默认值0，插入时不需要手动传入该参数，避免不必要的传值错误。

内容的提问来源于stack exchange，提问作者Asim