possible failures due to stats collector not updating fast enough under
heavy load. Per report from Jeremy Yoder.
# The sixth group of parallel test
# ----------
# "plpgsql" cannot run concurrently with "rules"
-test: limit plpgsql copy2 temp domain rangefuncs prepare without_oid conversion truncate alter_table sequence polymorphism stats
+test: limit plpgsql copy2 temp domain rangefuncs prepare without_oid conversion truncate alter_table sequence polymorphism
+
+# run stats by itself because its delay may be insufficient under heavy load
+test: stats