mongodb/jstests/aggregation/bugs/server26462.js

// Tests that adding a field that only contains metadata does not cause a segmentation fault when
// grouping on the added field.
(function() {
    "use strict";

    // Drop the old test collection, if any.
    db.server26462.drop();

    // Insert some test documents into the collection.
    assert.writeOK(db.server26462.insert({"_id": 1, "title": "cakes and ale"}));
    assert.writeOK(db.server26462.insert({"_id": 2, "title": "more cakes"}));
    assert.writeOK(db.server26462.insert({"_id": 3, "title": "bread"}));
    assert.writeOK(db.server26462.insert({"_id": 4, "title": "some cakes"}));

    // Create a text index on the documents.
    assert.commandWorked(db.server26462.createIndex({title: "text"}));

    // Add a metadata only field in the aggregation pipeline and use that field in the $group _id.
    let res = db.server26462
                  .aggregate([
                      {$match: {$text: {$search: "cake"}}},
                      {$addFields: {fooScore: {$meta: "textScore"}}},
                      {$group: {_id: "$fooScore", count: {$sum: 1}}}
                  ])
                  .itcount();

    // Assert that the command worked.
    assert.eq(2, res);
})();