Mongo aggregation with paginated data and totals

If you have a lot of events, {$ push: "$$ ROOT"}, will make Mongo return an error, I have solved it with $facet (Only works with version 3.4+)

aggregate([    { $match: options },    {      $facet: {        edges: [          { $sort: sort },          { $skip: skip },          { $limit: limit },        ],        pageInfo: [          { $group: { _id: null, count: { $sum: 1 } } },        ],      },    },  ])

Did this in two steps instead of one:

// Get the totalsdb.mongoAuditEvent.aggregate([{$group: {_id: "$corrId"}}, {$group: {_id: 1, total: {$sum: 1}}}]);// Get the datadb.mongoAuditEvent.aggregate([  {$group: {    _id : "$corrId",     currentEvent: {"$last": "$event.status"},     "events": { $push: "$$ROOT"}  }},  {$sort: {"events.timestamp": -1} }, // Latest first  {$skip: 0 },  {$limit: 10}], {allowDiskUse: true}).pretty();

I would be very happy if anybody got a better solution to this though.

A performance optimization tip:

When you use $facet stage for pagination, Try to add it as soon as it's possible.

For example: if you want to add $project or $lookup stage, add them after $facet, not before it.

it will have impressive effect in aggregation speed. because $project stage require MongoDB to explore all documents and get involve with all fields(which is not necessary).