To ensure as stable WiredTiger statsistics as possible, as those influence the plan chosen by the join order optimizer, in tpch_dataset.py we make the entire mongod instance read-only. However, we unlock the instance only in runPlanStabilityCommands , so the database is never unlocked after jstests/query_golden/join_opt/plan_stability_subjoin_cardinality_md.js has run.

To avoid running into this issue in the future, the lock/unlock calls should somehow be made symmetrical and the unlock should be made unavoidable.