const coll = db.coll; coll.drop(); const q = [{$sort : {a : 1}}, {$match : {t : 1}}]; const docs = []; for (let i = 0; i < 100; i++) { docs.push({}); } assert .commandWorked(coll.insert(docs)); assert .commandWorked(coll.createIndex({a: 1})) assert .commandWorked(coll.createIndex({t: 1})) jsTestLog(coll.explain().aggregate(q)) // with featureFlagCostBasedRanker: off, it shows 1 winning plan, 1 rejected // with featureFlagCostBasedRanker: on, it shows 1 winning plan, 0 rejected