Scala 如何使用新的Slick 2.0 HList来克服22列限制？

我目前正在编写流畅的代码，目标是一个有两个表>22列的旧模式。我该怎么办？在Scala 2.10.3下，2.0-M3在其他方面运行良好。 下面是我目前用于case类/元组的语法。我该怎么办

case类Joiner(
id:Int，
名称：选项[字符串]，
联系人：选项[字符串]
)
类Joiner（tag:tag）扩展表[Joiner]（tag，“Joiner”）{
def id=列[Int]（“id”，O.PrimaryKey，O.AutoInc，O.DBType（“Int（11）”）
def name=column[Option[String]（“name”，O.DBType（“varchar（255）”）
def contact=column[Option[String]（“contact”，O.DBType（“text”））
def*=（id、姓名、联系人）（Joiner.tuple、Joiner.unapply）
}
val joiners=TableQuery[joiners]

---

我在示例中没有看到任何内容，在最新更新的文档中只有一个简短的提及。我是Scala的新手，而且很圆滑。

定义

Scala>=2.10.4-RC2时（也由Slick 2.0.0代码生成器发出）：

上述情况导致Scala 2.10.3/2.10.4-RC1中的编译时间呈指数级增长。由于编译时间过长，超过26列不可行

无需映射到case类的Scala 22的变通方法（Scala 2.10中的最大字段限制为22）

---

另外：不要使用O.Nullable。改用

列[选项[字符串]]

。这段代码是为了演示在Scala v2.10.4_RC1中，当列数超过26列时仍然影响编译器的性能问题（它只是卡住了）

import java.sql.Timestamp
import scala.slick.driver.MySQLDriver.simple._
import scala.slick.collection.heterogenous._
// **** Uncomment this ****
//import scala.slick.collection.heterogenous.syntax._  



object DealSlick {


    class Deals(tag: Tag) extends Table[
      Long :: String :: String :: Option[String] :: Option[String] :: Option[String] ::
      // urlKeywords
      Option[String] :: Option[String] :: Option[String] :: Option[String] :: Option[String] ::
      // extTags
      Option[String] :: Option[String] :: Option[String] :: Option[String] :: Option[String] :: 
      // currency
      Option[String] :: Option[String] :: 
      // price
      Option[Double] :: Option[Double] :: Option[Double] :: Option[Double] ::
      // extStatus
      Option[String] :: Option[String] :: Option[Int] :: Option[Int] ::

     /* If you add more columns the compiler get stuck in a never-ending
      * compilation possibly related to 
      * https://github.com/slick/slick/issues/577
      */

     // endAt
     Option[Timestamp] :: /*Option[Timestamp] :: Option[Timestamp] :: Option[Timestamp] ::
     // timeZoneOffset
     Option[Int] :: Option[String] :: Option[Timestamp] :: Option[String] ::
     // locationName
     Option[String] :: Option[String] :: Option[String] :: Option[String] ::
     // city
     Option[String] :: Option[String] :: Option[String] :: Option[String] :: Option[String] :: 
     // latitude
     Option[Double] :: Option[Double] :: 
     // merchantTitle
     Option[String] :: */
     // End of list
     HNil
     ](tag, "deal") {
     def                id = column[Long]("id", O.PrimaryKey)
     def          siteName = column[String]("partner_site_name", O.NotNull)
     def        siteDomain = column[String]("partner_site_domain", O.NotNull)
     def    localeLanguage = column[Option[String]]("deal_language") 
     def     localeCountry = column[Option[String]]("deal_country") 
     def             extId = column[Option[String]]("deal_ext_id") 
     def       urlKeywords = column[Option[String]]("deal_url_keywords") 
     def          keywords = column[Option[String]]("deal_keywords") 
     def     extCategories = column[Option[String]]("deal_ext_categories") 
     def      categoryText = column[Option[String]]("deal_category_text") 
     def          coverage = column[Option[String]]("deal_coverage") 
     def           extTags = column[Option[String]]("deal_ext_tags") 
     def             title = column[Option[String]]("deal_title") 
     def       description = column[Option[String]]("deal_description")
     def          extImage = column[Option[String]]("deal_ext_image") 
     def               url = column[Option[String]]("deal_url") 
     def          currency = column[Option[String]]("deal_currency") 
     def       currencySym = column[Option[String]]("deal_currency_sym") 
     def             price = column[Option[Double]]("deal_price") 
     def            saving = column[Option[Double]]("deal_saving") 
     def          discount = column[Option[Double]]("deal_discount") 
     def            dvalue = column[Option[Double]]("deal_value") 
     def         extStatus = column[Option[String]]("deal_ext_status") 
     def            status = column[Option[String]]("deal_status") 
     def           soldQty = column[Option[Int]]("deal_sold_qty") 
     def           leftQty = column[Option[Int]]("deal_left_qty") 
     def             endAt = column[Option[Timestamp]]("deal_end_at") 
 /*    def          endAtUtc = column[Option[Timestamp]]("deal_end_at_utc") 
     def         expiresAt = column[Option[Timestamp]]("deal_expires_at") 
     def      expiresAtUtc = column[Option[Timestamp]]("deal_expires_at_utc") 
     def    timeZoneOffset = column[Option[Int]]("time_zone_offset") 
     def      timeZoneName = column[Option[String]]("time_zone_name")
     def       timeGrabbed = column[Option[Timestamp]]("time_grabbed") 
     def  timeRemainingStr = column[Option[String]]("time_remaining_str") 
     def      locationName = column[Option[String]]("location_name")
     def           address = column[Option[String]]("location_address") 
     def            street = column[Option[String]]("location_street") 
     def        postalCode = column[Option[String]]("location_postalcode")
     def              city = column[Option[String]]("location_city") 
     def          province = column[Option[String]]("location_province") 
     def            region = column[Option[String]]("location_region") 
     def             state = column[Option[String]]("location_state") 
     def           country = column[Option[String]]("location_country") 
     def          latitude = column[Option[Double]]("location_latitude") 
     def         longitude = column[Option[Double]]("location_longitude") 
     def     merchantTitle = column[Option[String]]("merchant_title") 

*/
def * = (id :: siteName :: siteDomain :: localeLanguage :: localeCountry :: extId :: 
         urlKeywords :: keywords :: extCategories :: categoryText :: coverage :: 
         extTags :: title :: description :: extImage :: url ::
         currency :: currencySym :: price :: saving :: discount :: dvalue ::
         extStatus :: status :: soldQty :: leftQty ::
         endAt :: /*endAtUtc :: expiresAt :: expiresAtUtc ::
         timeZoneOffset :: timeZoneName :: timeGrabbed :: timeRemainingStr ::
         locationName :: address :: street :: postalCode :: 
         city :: province :: region :: state :: country ::
         latitude :: longitude ::
         merchantTitle :: */
         HNil )  
   }

}

**更新** 在更新到Scala 2.10.4-RC2后，编译器在编译过程中会进一步执行一些步骤，但它再次陷入困境：

以下是仅定义少数表列时的编译器输出

[信息][加载的类文件/Users/max/.ivy2/cache/com.typesafe.slick/slick_2.10/jars/slick_2.10-2.0.0.jar（scala/slick/backend/DatabaseComponent.class）以1ms为单位]

[info][loaded class file/Users/max/.ivy2/cache/com.typesafe.slick/slick_2.10/jars/slick_2.10-2.0.0.jar（scala/slick/lifted/ShapedValue.class）以2ms为单位]

---

[info][loaded package loader util in 2ms]当使用超过26列时，此输出不会打印在屏幕上

如果我不使用case类，我可以定义一个常规类，还是需要在某种列表中列出所有类型？另外，对于“*”投影中的选项列，我是否仍然使用尾随的“？”，或者这是推断的？。？也可以说是推断出来的。你不需要它们。我不确定你所说的列出所有类型是什么意思，但是你可以把你的行映射到任何东西。概念是

（factoryFunction，extractorFunction）

我应该用什么来代替case类，因为在Scala 2.11之前，case类只限于22列？如何将过去的case类声明为HList，并将其作为类型参数传递给table类？我更新示例以显示类型。关于case类，您可以省略它。您将无法按结果中的名称访问列，只能按位置

r（2）

。如果您确实想要命名访问，您可以通过编写适当的工厂和提取器函数映射到

中的普通类。根据Vogt先生的建议更正。也张贴在这里：请在将来交叉链接。对不起，我收到一条消息，我的Google Groups帖子被拒绝，因此我认为它不起作用。注意：如果有人试图遵循此解决方案（如下）截至Slick 2.0-M3，HList代码无法工作——编译超过22列（以指数形式增长）将需要数小时和千兆字节的RAM，以确保实现是正确的（据我们所知）。然而，目前它似乎在Scala编译器中触发了指数级编译时间，对于25或更大的大小，这会严重影响您。我们将研究如何解决这个问题。这可能是从RC1开始解决的，但我不确定。我试图跟踪我在中看到的提交和bug跟踪消息，但无法跟踪。如果你想修补Scala或者自己光滑一些，有一些修复方法。Christopher，谢谢你的提示，但是我已经试过Scala v2.10.4-RC2了，我必须说我注意到编译器在这一点上不再阻塞，但它在下一步会被卡住。如果您和您的团队认为值得对此问题进行调查，您可以使用我发布的代码进行测试。

import scala.slick.collection.heterogenous._
import syntax._
class Joiners(tag: Tag) extends Table[
    Int :: Option[String] :: Option[String] :: HNil
](tag, "joiner") {
  ...
  def * = id :: name :: contact :: HNil
}

import scala.slick.collection.heterogenous._
import syntax._
class Joiners(tag: Tag) extends Table[
    HCons[Int, HCons[Option[String], HCons[Option[String], HNil]]]
](tag, "joiner") {
  ...
  def * = id :: name :: contact :: HNil
}

Joiners.run.map( r => r(2) ) // Gets column contact. It's typesafe. .apply is a macro. Only works for literals not for variables as positions.

import java.sql.Timestamp
import scala.slick.driver.MySQLDriver.simple._
import scala.slick.collection.heterogenous._
// **** Uncomment this ****
//import scala.slick.collection.heterogenous.syntax._  



object DealSlick {


    class Deals(tag: Tag) extends Table[
      Long :: String :: String :: Option[String] :: Option[String] :: Option[String] ::
      // urlKeywords
      Option[String] :: Option[String] :: Option[String] :: Option[String] :: Option[String] ::
      // extTags
      Option[String] :: Option[String] :: Option[String] :: Option[String] :: Option[String] :: 
      // currency
      Option[String] :: Option[String] :: 
      // price
      Option[Double] :: Option[Double] :: Option[Double] :: Option[Double] ::
      // extStatus
      Option[String] :: Option[String] :: Option[Int] :: Option[Int] ::

     /* If you add more columns the compiler get stuck in a never-ending
      * compilation possibly related to 
      * https://github.com/slick/slick/issues/577
      */

     // endAt
     Option[Timestamp] :: /*Option[Timestamp] :: Option[Timestamp] :: Option[Timestamp] ::
     // timeZoneOffset
     Option[Int] :: Option[String] :: Option[Timestamp] :: Option[String] ::
     // locationName
     Option[String] :: Option[String] :: Option[String] :: Option[String] ::
     // city
     Option[String] :: Option[String] :: Option[String] :: Option[String] :: Option[String] :: 
     // latitude
     Option[Double] :: Option[Double] :: 
     // merchantTitle
     Option[String] :: */
     // End of list
     HNil
     ](tag, "deal") {
     def                id = column[Long]("id", O.PrimaryKey)
     def          siteName = column[String]("partner_site_name", O.NotNull)
     def        siteDomain = column[String]("partner_site_domain", O.NotNull)
     def    localeLanguage = column[Option[String]]("deal_language") 
     def     localeCountry = column[Option[String]]("deal_country") 
     def             extId = column[Option[String]]("deal_ext_id") 
     def       urlKeywords = column[Option[String]]("deal_url_keywords") 
     def          keywords = column[Option[String]]("deal_keywords") 
     def     extCategories = column[Option[String]]("deal_ext_categories") 
     def      categoryText = column[Option[String]]("deal_category_text") 
     def          coverage = column[Option[String]]("deal_coverage") 
     def           extTags = column[Option[String]]("deal_ext_tags") 
     def             title = column[Option[String]]("deal_title") 
     def       description = column[Option[String]]("deal_description")
     def          extImage = column[Option[String]]("deal_ext_image") 
     def               url = column[Option[String]]("deal_url") 
     def          currency = column[Option[String]]("deal_currency") 
     def       currencySym = column[Option[String]]("deal_currency_sym") 
     def             price = column[Option[Double]]("deal_price") 
     def            saving = column[Option[Double]]("deal_saving") 
     def          discount = column[Option[Double]]("deal_discount") 
     def            dvalue = column[Option[Double]]("deal_value") 
     def         extStatus = column[Option[String]]("deal_ext_status") 
     def            status = column[Option[String]]("deal_status") 
     def           soldQty = column[Option[Int]]("deal_sold_qty") 
     def           leftQty = column[Option[Int]]("deal_left_qty") 
     def             endAt = column[Option[Timestamp]]("deal_end_at") 
 /*    def          endAtUtc = column[Option[Timestamp]]("deal_end_at_utc") 
     def         expiresAt = column[Option[Timestamp]]("deal_expires_at") 
     def      expiresAtUtc = column[Option[Timestamp]]("deal_expires_at_utc") 
     def    timeZoneOffset = column[Option[Int]]("time_zone_offset") 
     def      timeZoneName = column[Option[String]]("time_zone_name")
     def       timeGrabbed = column[Option[Timestamp]]("time_grabbed") 
     def  timeRemainingStr = column[Option[String]]("time_remaining_str") 
     def      locationName = column[Option[String]]("location_name")
     def           address = column[Option[String]]("location_address") 
     def            street = column[Option[String]]("location_street") 
     def        postalCode = column[Option[String]]("location_postalcode")
     def              city = column[Option[String]]("location_city") 
     def          province = column[Option[String]]("location_province") 
     def            region = column[Option[String]]("location_region") 
     def             state = column[Option[String]]("location_state") 
     def           country = column[Option[String]]("location_country") 
     def          latitude = column[Option[Double]]("location_latitude") 
     def         longitude = column[Option[Double]]("location_longitude") 
     def     merchantTitle = column[Option[String]]("merchant_title") 

*/
def * = (id :: siteName :: siteDomain :: localeLanguage :: localeCountry :: extId :: 
         urlKeywords :: keywords :: extCategories :: categoryText :: coverage :: 
         extTags :: title :: description :: extImage :: url ::
         currency :: currencySym :: price :: saving :: discount :: dvalue ::
         extStatus :: status :: soldQty :: leftQty ::
         endAt :: /*endAtUtc :: expiresAt :: expiresAtUtc ::
         timeZoneOffset :: timeZoneName :: timeGrabbed :: timeRemainingStr ::
         locationName :: address :: street :: postalCode :: 
         city :: province :: region :: state :: country ::
         latitude :: longitude ::
         merchantTitle :: */
         HNil )  
   }

}