This repro requires the changes of SERVER-116987 db.foo.drop() const docs = [] const kNumDocs = 15000 for (let i = 0; i < kNumDocs; i++) {     docs.push({a: i, b: i}); } docs.push({a: 7000 + 1, b: 7000 + 1, c: 1}); docs.push({a: 8000 + 1, b: 8000 + 1, c: 1}); db.foo.insertMany(docs); db.foo.createIndexes([{a: 1}, {b: 1}]); db.adminCommand({setParameter: 1, planRankerMode: "automaticCE" }) db.adminCommand({setParameter: 1, automaticCEPlanRankingStrategy: "CBRForNoMultiplanningResults" }) // puts plan into cache, with 3 "works" but it should be 4 to represent the 2 keys examined + 2 docs examined db.foo.aggregate([{$match: {a: 5, b: 10}}, {$group: {_id: "$a" , avg: {$avg: "$x" }}}]) // activates plan db.foo.aggregate([{$match: {a: 5, b: 10}}, {$group: {_id: "$a" , avg: {$avg: "$x" }}}]) db.foo.aggregate([{$match: {a: 5, b: 10}}, {$group: {_id: "$a" , avg: {$avg: "$x" }}}]) // tassert! "errmsg" : "Expected variant to hold numReads" , "code" : 8908810,