Notify the queue runner when a build is deleted

src/sql/hydra.sql

@@ -202,6 +202,22 @@ create table Builds (
 );
 
 
+#ifdef POSTGRESQL
+
+create function notifyBuildDeleted() returns trigger as $$
+  begin
+    execute 'notify builds_deleted';
+    return null;
+  end;
+$$ language plpgsql;
+
+create trigger BuildDeleted after delete on Builds
+  for each row
+  execute procedure notifyBuildDeleted();
+
+#endif
+
+
 create table BuildOutputs (
     build         integer not null,
     name          text not null,