Given a simple timeseries collection:

./build/install/bin/mongod --setParameter featureFlagSbeFull=true
> db.coll.drop()
> db.createCollection("coll", {timeseries: {timeField: "t"}})
> db.coll.insert({t: new Date(), a: 4, b: 7, c: 5})
> db.coll.insert({t: new Date(), a: 2, b: 9, c: 8})
> db.coll.insert({t: new Date(), a: 3, b: 1, c: 6})

the goals of this task are to make the following query work in block-processing mode and to write a jstest that verifies it works:

db.coll.aggregate([{$project: {a: 1}}, {$group: {_id: null, x: {$sum : "$a"}}}], {allowDiskUse: false})

Note that block processing is not yet supported with allowDiskUse: true, which has been the default since 6.0. This is being addressed in SERVER-84781.

Before this task the SBE plan for this query is

TBD           

The integration test written for this ticket should verify both correctness and that $sum actually uses the block processing code path where expected.