ScalaQuery爲什麼不爲外鍵創建ddl？

我有以下使用ScalaQuery表定義0.10.0-M1：ScalaQuery爲什麼不爲外鍵創建ddl？

import org.scalaquery.ql.basic.{ BasicTable => Table } 

object Nodes extends Table[(String, String)]("node") { 
    def id = column[String]("id", O.PrimaryKey) 
    def name = column[String]("name", O.NotNull) 

    def * = id ~ name 
    private def uName = index("uk_name", name, unique = true) 
} 

object Links extends Table[(String, String, String, String)]("link") { 
    def id = column[String]("id", O.PrimaryKey) 
    def from = column[String]("from_id", O.NotNull) 
    def link = column[String]("name", O.NotNull) 
    def to = column[String]("to_id", O.NotNull) 

    def * = id ~ from ~ link ~ to 
    private def ukFromLinkTo = index("uk_FromLinkTo", from ~ link ~ to, unique = true) 
    private def fkFrom = foreignKey("fk_Link_Node_From", from, Nodes)(_.id) 
    private def fkTo = foreignKey("fk_Link_Node_To", to, Nodes)(_.id) 
}

但是使用這個片段創建時（印刷）的DDL：

val db = Database.forURL("jdbc:h2:mem:test1;DB_CLOSE_DELAY=-1", driver = "org.h2.Driver") 

db withSession { 
    val ddl = (Nodes.ddl ++ Links.ddl) 
    ddl.create 
    println(ddl.createStatements.mkString("\n")) 
}

沒有外鍵獲取生成，也不打印。

這是爲什麼？我該如何解決它？

來源

2012-06-17 Jens Schauder