LQO 0.5.0 adds row-count hints for servers with the pg_hint_plan extension. LQO already times each query’s default plan with EXPLAIN ANALYZE, so it knows how many rows each join really produced. Where the planner’s estimate was more than 2 times off, it writes a pg_hint_plan hint that corrects it and lets PostgreSQL plan again. That’s for queries that need different joins in different places, where switching one method off for the whole query does as much harm as good.
The hints are judged by the same rule as the planner switches, and lqo serve can apply a proven one to live queries. On the demo they took about a third off the trap query, and switching off nested loops took more than half, so that’s what LQO suggested. Without pg_hint_plan, nothing changes.