src/Pure/General/sql.scala

         catch { case exn: Throwable => connection.rollback(savepoint); throw exn }
       }
       finally { connection.setAutoCommit(auto_commit) }
     }
 
-    private var _transaction_count: Int = 0
-    private def transaction_count(): Int =
-      synchronized { _transaction_count += 1; _transaction_count }
-
     def transaction_lock[A](
       tables: Tables,
       create: Boolean = false,
       label: String = "",
       log: Logger = new System_Logger

           case "true" => Time.min
           case "false" | "" => Time.max
           case s => error("Bad system property " + prop + ": " + quote(s))
         }
 
-      val trace_count = transaction_count()
+      val trace_count = - SQL.transaction_count()
       val trace_start = Time.now()
       var trace_nl = false
 
       def trace(msg: String, nl: Boolean = false): Unit = {
         val trace_time = Time.now() - trace_start

       if (strict || !tables.contains(table.name)) {
         execute_statement("CREATE VIEW " + table + " AS " + { table.query; table.body })
       }
     }
   }
+
+
+  private val transaction_count = Counter.make()
 }
 
 
 
 /** SQLite **/