postgresql for update sample

src/main/scala/Driver.scala

@@ -0,0 +1,52 @@
+package myapp
+
+import slick.driver.PostgresDriver
+
+trait MyPostgresDriver extends PostgresDriver
+    with PgForUpdateSupport
+{
+  override val simple = new SimpleQLPlus {}
+
+  trait SimpleQLPlus extends SimpleQL
+      with ForUpdateTableImplicits
+}
+
+object MyPostgresDriver extends MyPostgresDriver
+
+trait PgForUpdateSupport extends PostgresDriver { driver =>
+  import scala.slick.ast.{Comprehension, Node, Symbol, TableNode}
+  import scala.slick.compiler.CompilerState
+
+  trait ForUpdateTable
+
+  trait ForUpdateTableImplicits {
+    type ForUpdateTable = driver.ForUpdateTable
+  }
+
+  class QueryBuilder(tree: Node, state: CompilerState) extends super.QueryBuilder(tree, state) {
+    import scala.slick.util.MacroSupport.macroSupportInterpolation
+
+    override protected def buildComprehension(c: Comprehension): Unit = {
+      super.buildComprehension(c)
+      buildForUpdateClause(c.from)
+    }
+
+    protected def buildForUpdateClause(from: Seq[(Symbol, Node)]) = building(FromPart) {
+      val forUpdateFrom = from.filter { case (_, n) =>
+        n match {
+          case TableNode(_, _, _, driverTable, _) =>
+            driverTable.isInstanceOf[ForUpdateTable]
+          case _ => false
+        }
+      }
+      if(!forUpdateFrom.isEmpty) {
+        b" for update of "
+        b.sep(forUpdateFrom , ", ") { case (sym, n) =>
+          b += symbolName(sym)
+        }
+      }
+    }
+  }
+  override def createQueryBuilder(n: Node, state: CompilerState): QueryBuilder = new QueryBuilder(n, state)
+}
+

src/main/scala/main.scala

@@ -1,6 +1,6 @@
 package myapp
 
-import scala.slick.driver.PostgresDriver.simple._
+import MyPostgresDriver.simple._
 import scala.util.control.Exception._
 
 object MyApp extends App{
@@ -31,12 +31,15 @@ object MyApp extends App{
   }
   val coffees = TableQuery[Coffees]
 
+  class CoffeesForUpdate(tag: Tag) extends Coffees(tag) with ForUpdateTable
+  val coffeesForUpdate = TableQuery[CoffeesForUpdate]
+
   Database.forURL("jdbc:postgresql:test1", driver = "org.postgresql.Driver") withSession {
     implicit session =>
 
       allCatch opt (suppliers.ddl ++ coffees.ddl).create
       val q = for {
-        c <- coffees if c.price < 9.0
+        c <- coffeesForUpdate if c.price < 9.0
         s <- suppliers if s.id === c.supID
       } yield (c.name, s.name)
       q.list