diff -r d7cefedbca94 -r 0c44e3e9126f src/Pure/General/postgresql.scala
--- a/src/Pure/General/postgresql.scala	Wed Feb 08 21:06:47 2017 +0100
+++ b/src/Pure/General/postgresql.scala	Wed Feb 08 22:11:37 2017 +0100
@@ -12,9 +12,6 @@
 
 object PostgreSQL
 {
-  /** database connection **/
-
-  val default_host = "localhost"
   val default_port = 5432
 
   def open_database(
@@ -34,7 +31,7 @@
     new Database(spec, connection)
   }
 
-  class Database private[PostgreSQL](spec: String, val connection: Connection)
+  class Database private[PostgreSQL](spec: String, val connection: Connection) extends SQL_Database
   {
     override def toString: String = spec
   }