Question

如何使用光滑执行以下操作：

select * from users where location = 3 and (permissions & 4 = 4);

这可能吗？还是我必须使用原始sql？

Answer 1

如果您的数据库支持SQL运算符，您可以为其定义Slick运算符，如下所述：http://slick.typesafe.com/doc/2.1.0/userdefined.html

Answer 2

通过遵循数字运算符

的模式，我能够使按位运算符工作

in ... / util / slick / BitwiseExtension.scala

package ...util.slick

import slick.ast.Library.SqlOperator
import slick.lifted.{BaseExtensionMethods, ExtensionMethods, Rep}

object Library {
  val & = new SqlOperator("&")
}

trait BitwiseColumnExtensionMethods[B1, P1] extends Any with ExtensionMethods[B1, P1] {
  def & [P2, R](e: Rep[P2])(implicit om: o#arg[B1, P2]#to[B1, R]) =
    om.column(Library.&, n, e.toNode)
}

final class BaseBitwiseColumnExtensionMethods[P1](val c: Rep[P1]) extends AnyVal
  with BitwiseColumnExtensionMethods[P1, P1]
  with BaseExtensionMethods[P1]

in ... / util / slick / package.scala

package ...util

import slick.ast.{ BaseTypedType, NumericTypedType }
import slick.lifted.Rep

package object slick {
  implicit def bitwiseColumnExtensionMethods[B1](c: Rep[B1])(implicit tm: BaseTypedType[B1] with NumericTypedType) = new BaseBitwiseColumnExtensionMethods[B1](c)
}

然后在查询中使用它：

import ...util._

Tables.users.filter({ r =>
    (r.permissions & mask) === mask
})

您可以通过查看JdbcStatementBuilderComponent（https://github.com/slick/slick/blob/6c638ea0688345044e3d3a362fab92c76db9a85b/slick/src/main/scala/slick/jdbc/JdbcStatementBuilderComponent.scala#L378）

来了解Slick如何生成查询

case Apply(sym: Library.SqlOperator, ch) =>
  b"\("
  if(ch.length == 1) {
    b"${sym.name} ${ch.head}"
  } else b.sep(ch, " " + sym.name + " ")(expr(_))
  b"\)"

使用光滑的按位操作

2 个答案: