我有以下表格:
@Entity(
tableName = "users"
)
class Users {
@PrimaryKey(autoGenerate = true)
var id: Long? = null
@NonNull
var name: String? = null
}
@Entity(
tableName = "pets",
foreignKeys = [
ForeignKey(
entity = Users::class,
parentColumns = ["id"],
childColumns = ["owner_id"],
onDelete = ForeignKey.CASCADE
)
]
)
class Pets {
@PrimaryKey(autoGenerate = true)
var id: Long? = null
@NonNull
var name: String? = null
@ColumnInfo(name = "owner_id")
var ownerId: Long? = null
}
当我运行删除所有用户表行的迁移时,宠物表不受影响。行不会自动删除。
object Migration_1_2 : Migration(1, 2) {
override fun migrate(database: SupportSQLiteDatabase) {
database.execSQL("""
DELETE FROM users
""")
}
}
即使我在迁移之前执行以下代码 fragment ,它也不起作用。
database.execSQL("PRAGMA foreign_keys=ON;");
我应该怎么做才能使 onDelete = ForeignKey.CASCADE
正常工作?
最佳答案
正如@sergiytikhonov 在他的评论中指出的那样,在迁移函数中启用 foreign_keys 约束没有任何效果。这是因为 migrations are executed as part of a transaction和 the pragma is a no-op inside a transaction .
在执行迁移之前,我看不到有任何方法可以控制和启用 foreign_keys
。我认为您唯一的选择是在迁移过程中明确删除宠物:
override fun migrate(database: SupportSQLiteDatabase) {
database.execSQL("""
DELETE FROM pets WHERE owner_id IN (SELECT id FROM users)
""")
database.execSQL("""
DELETE FROM users
""")
}
关于android - 房间的 `onDelete = CASCADE` 在迁移期间不工作,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/62064932/