Slick 3.0.0 database agnostism

Question

I started to use Slick 3.0.0 and I like it's succinct syntax. Nevertheless, I wasn't able to find a way to use it in a database agnostic way.

In the following example provided in the documentation: http://slick.typesafe.com/doc/3.0.0/gettingstarted.html

I'd like to be able to decouple somehow this code of the database used and avoid importing database specific in my code (i.e slick.driver.H2Driver.api._).

I tried to get rid of it by providing the connection using the cake pattern, but the ".result" member isn't available then.

A workaround would be to import slick.driver.JdbcDriver.api._, but it is deprecated and thus should not be a good starting point.

Anyone found a way to use Slick 3.0.0 in a database agnostic and elegant way?

This question isn't far of "How to write database-agnostic Play application and perform first-time database initialization?", but that one focuses on Slick 3.0.0. Sadely the answers provided with that former question aren't targetting Slick 3.0.0 except one which uses deprecated code.

If you use basic/standard SQL, I guess you can use native queries in a way it would be easy to switch to another RDBMS (do you really need to?). — cchantep
Thanks @cchantep, you mean using the plain SQL queries of Slick (slick.typesafe.com/doc/3.0.0/sql.html)? About your question, yes I like to switch of RDBMS for some unit tests (where is use h2) and also I'd like to love to be able to change without having to rebuild my app. — raphael
If that's just for unit testing, you do not really need agnostic calls, but to be able to simulate the same DB behaviour, either with in-memory DB or using JDBC testing framework (like acolyte.eu.org ). — cchantep
This seems to be a duplicate of: stackoverflow.com/q/13661339/13822 — triggerNZ
@cchantep, then you suggest do use the specific driver of my RDBMS (in my case PostgreSQL) over an in-memory DB (i.e. H2) for unit testing? — raphael

dwickern dwickern · Accepted Answer · 2015-06-30T01:43:46

The slick driver class you're looking for is slick.driver.JdbcProfile.

There's an official example project slick-multidb which you can obtain through activator (github). Here's the relevant code:

import scala.language.higherKinds
import slick.driver.JdbcProfile

/** All database code goes into the DAO (data access object) class which
  * is parameterized by a Slick driver that implements JdbcProfile.
  */
class DAO(val driver: JdbcProfile) {
  // Import the Scala API from the driver
  import driver.api._

  class Props(tag: Tag) extends Table[(String, String)](tag, "PROPS") {
    def key = column[String]("KEY", O.PrimaryKey)
    def value = column[String]("VALUE")
    def * = (key, value)
  }
  val props = TableQuery[Props]

  /** Create the database schema */
  def create: DBIO[Unit] =
    props.ddl.create

  /** Insert a key/value pair */
  def insert(k: String, v: String): DBIO[Int] =
    props += (k, v)

  /** Get the value for the given key */
  def get(k: String): DBIO[Option[String]] =
    (for(p <- props if p.key === k) yield p.value).result.headOption

  /** Get the first element for a Query from this DAO */
  def getFirst[M, U, C[_]](q: Query[M, U, C]): DBIO[U] =
    q.result.head
}

Client code:

val dao = new DAO(H2Driver)
import dao.driver.api._
db.run(dao.insert("foo", "bar"))

Slick 3.0.0 database agnostism

1 Answers