我需要从主 - 细节关系中收集报告数据。这是一个简化的例子：
case class Person(id: Int, name: String)
case class Order(id: String, personId: Int, description: String)
class PersonTable(tag: Tag) extends Table[Person](tag, "person") {
def id = column[Int]("id")
def name = column[String]("name")
override def * = (id, name) <>(Person.tupled, Person.unapply)
}
class OrderTable(tag: Tag) extends Table[Order](tag, "order") {
def id = column[String]("id")
def personId = column[Int]("personId")
def description = column[String]("description")
override def * = (id, personId, description) <>(Order.tupled, Order.unapply)
}
val persons = TableQuery[PersonTable]
val orders = TableQuery[OrderTable]
case class PersonReport(nameToDescription: Map[String, Seq[String]])
/** Some complex function that cannot be expressed in SQL and
* in slick's #join.
*/
def myScalaCondition(person: Person): Boolean =
person.name.contains("1")
// Doesn't compile:
// val reportDbio1:DBIO[PersonReport] =
// (for{ allPersons <- persons.result
// person <- allPersons
// if myScalaCondition(person)
// descriptions <- orders.
// filter(_.personId == person.id).
// map(_.description).result
// } yield (person.name, descriptions)
// ).map(s => PersonReport(s.toMap))
val reportDbio2: DBIO[PersonReport] =
persons.result.flatMap {
allPersons =>
val dbios = allPersons.
filter(myScalaCondition).map { person =>
orders.
filter(_.personId == person.id).
map(_.description).result.map { seq => (person.name, seq) }
}
DBIO.sequence(dbios)
}.map(ps => PersonReport(ps.toMap))
它看起来很遥远。当我需要收集3个级别的主细节数据时，它变得难以理解。
有更好的方法吗？