import {ShardingTest} from "jstests/libs/shardingtest.js" ; // Using chunkSize=1 is not necessary to repro the issue, but makes it easier since we need less documents to get data on both shards. const st = new ShardingTest({shards: 2, other: {chunkSize: 1}}); const sDB = st.s.getDB( 'test' ); assert (sDB.coll.drop()); assert .commandWorked(sDB.adminCommand({enableSharding: 'test' , primaryShard: st.shard0.shardName})); assert .commandWorked(sDB.adminCommand({ shardCollection: `test.coll`, key: {m: 1}, timeseries: {timeField: 't' , metaField: 'm' } })); const coll = sDB.coll; st.startBalancer(); // Insert some docs const alphabet = 'abcdefghijklmnop' ; const docs = []; for (let i = 0; i < 100; i++){ docs.push({t: new Date(i * 1000), m: i % 100, otherField: alphabet.repeat(1000)}); } assert .commandWorked(coll.insert(docs)); // Let the balancer move documents so we have data on both shards st.awaitBalancerRound(); coll.aggregate([{$group: {_id: null , document_count: {$count: {}}, max_time: {$max: '$t' }}}]).toArray() // uassert 9961600: Unexpected type on the merging pass of the $sum. This likely happened due to a malformed query. st.stop();