import {configureFailPoint} from "jstests/libs/fail_point_util.js" ; const conn = MongoRunner.runMongod({}); const testDb = conn.getDB(jsTestName()); const coll = testDb.coll; const control = testDb.control; const filter = {$expr: {$eq: [ "$a" , 5]}}; const docs = []; for (let i = 0; i < 100; i++) { docs.push({a: 5, b: i, c: i}); } assert .commandWorked(coll.insert(docs)); assert .commandWorked(coll.createIndex({a: 1})); assert .commandWorked(coll.createIndex({a: 1, b: 1})); assert .commandWorked(coll.createIndex({a: 1, c: 1})); // Two concurrent finds multiplan against the pre-flip, non-multikey {a: 1} index and pause // inside the multiplanner. Both plan correctly (point bounds on a non-multikey index) and return // all 100 documents; the second one's cache write promotes the stale entry to active. const fp = configureFailPoint(conn, "sleepWhileMultiplanning" , {ms: 8000}); const shells = []; for (let i = 0; i < 2; i++) { shells.push(startParallelShell( ` const testDb = db.getSiblingDB( "${testDb.getName()}" ); assert .commandWorked(testDb.control.insert({_id: ${i}})); const n = testDb.coll.find(${tojson(filter)}).itcount(); assert .eq(100, n, "multiplanning find returned incomplete results" ); `, conn.port)); } // Wait until both finds are inside the multiplanner sleep. assert .soon(() => control.countDocuments({}) === 2, "parallel shells did not start" ); sleep(2000); // Flip {a: 1} to multikey while the finds are paused. This clears the plan cache inline in the // write unit of work, but both finds have already snapshotted the non-multikey IndexEntry and // will write their cache entries after the clear — a stale entry that nothing re-screens. assert .commandWorked(coll.insert({a: [1, 2, 3]})); fp.off(); shells.forEach((shell) => shell()); // The plan cache now holds an active stale entry tagged to the pre-flip index. Replaying it // builds an unfiltered index scan with empty bounds on the now-multikey index, so reads return // nothing. assert .eq(100, coll.find(filter).hint({$natural: 1}).itcount()); // Assertion fails assert .eq(100, coll.find(filter).itcount(), "find returned incomplete results from the plan cache" ); MongoRunner.stopMongod(conn);