mongo/jstests/aggregation/accumulators/concat_arrays.js

/**
 * Basic tests for the $concatArrays accumulator.
 * @tags: [requires_fcv_81]
 */
import {assertErrorCode} from "jstests/aggregation/extras/utils.js";

const coll = db["accumulators_concat_arrays"];
assert(coll.drop());

// Test that $concatArrays correctly concatenates arrays, preserves sort order and preserves order
// of the elements inside the concatenated arrays.
assert.commandWorked(
    coll.insert([
        {_id: 0, author: "Adrian", publisher: "Pub1", books: ["Adrian Book 0", "Adrian Book 1"]},
        {_id: 1, author: "Militsa", publisher: "Pub1", books: ["Militsa Book 0"]},
        {_id: 2, author: "Hana", publisher: "Pub1", books: ["Hana Book 0", "Hana Book 1"]},
    ]),
);

let result = coll
    .aggregate([
        {$match: {_id: {$in: [0, 1, 2]}}},
        {$sort: {_id: 1}},
        {$group: {_id: null, allBooks: {$concatArrays: "$books"}}},
    ])
    .toArray();

assert.eq(result, [
    {
        _id: null,
        allBooks: ["Adrian Book 0", "Adrian Book 1", "Militsa Book 0", "Hana Book 0", "Hana Book 1"],
    },
]);

// Redo the aggregation with the reverse sort to ensure sort order is really preserverd and we're
// not just looking at the docs in the order they are found in the collection.
result = coll
    .aggregate([
        {$match: {_id: {$in: [0, 1, 2]}}},
        {$sort: {_id: -1}},
        {$group: {_id: null, allBooks: {$concatArrays: "$books"}}},
    ])
    .toArray();

assert.eq(result, [
    {
        _id: null,
        allBooks: ["Hana Book 0", "Hana Book 1", "Militsa Book 0", "Adrian Book 0", "Adrian Book 1"],
    },
]);

// $concatArrays should concatenate arrays, and any nested arrays should remain array values.
assert.commandWorked(
    coll.insert({
        _id: 3,
        author: "Ben",
        publisher: "Pub2",
        books: [["Ben Series 0 Book 0", "Ben Series 0 Book 1"], ["Ben Series 1 Book 0"], "Ben Book 4"],
    }),
);
result = coll
    .aggregate([
        {$match: {_id: {$in: [1, 3]}}},
        {$sort: {_id: 1}},
        {$group: {_id: null, allBooks: {$concatArrays: "$books"}}},
    ])
    .toArray();
assert.eq(result, [
    {
        _id: null,
        allBooks: [
            "Militsa Book 0",
            ["Ben Series 0 Book 0", "Ben Series 0 Book 1"],
            ["Ben Series 1 Book 0"],
            "Ben Book 4",
        ],
    },
]);

// $concatArrays should 'skip over' documents that do not have field.
// Importantly, do not create a null element for documents that do not have the referenced field.
assert.commandWorked(
    coll.insert([
        {_id: 4, author: "Nick", publisher: "Pub3", books: ["Smile :)"]},
        {_id: 5, author: "Santiago", publisher: "Pub3"},
        {_id: 6, author: "Matt", publisher: "Pub3", books: ["Happy!"]},
    ]),
);
result = coll
    .aggregate([
        {$match: {_id: {$in: [4, 5, 6]}}},
        {$sort: {_id: 1}},
        {$group: {_id: null, allBooks: {$concatArrays: "$books"}}},
    ])
    .toArray();
assert.eq(result, [{_id: null, allBooks: ["Smile :)", "Happy!"]}]);

// Test for errors on non-array types ($concatArrays only supports arrays).
const notArrays = [1, "string", {object: "object"}, null];

for (const notAnArray of notArrays) {
    assert.commandWorked(
        coll.insert([
            {
                _id: "doesNotMatter",
                author: "doesNotMatter",
                publisher: "doesNotMatter",
                books: notAnArray,
            },
        ]),
    );

    assertErrorCode(coll, [{$group: {_id: null, allBooks: {$concatArrays: "$books"}}}], ErrorCodes.TypeMismatch);

    assert.commandWorked(coll.deleteOne({_id: "doesNotMatter"}));
}

// Basic test of $concatArrays with grouping.
result = coll
    .aggregate([
        {$match: {_id: {$in: [0, 1, 3]}}},
        {$sort: {_id: 1}},
        {$group: {_id: "$publisher", booksByPublisher: {$concatArrays: "$books"}}},
        {$sort: {_id: 1}},
    ])
    .toArray();
assert.eq(result, [
    {_id: "Pub1", booksByPublisher: ["Adrian Book 0", "Adrian Book 1", "Militsa Book 0"]},
    {
        _id: "Pub2",
        booksByPublisher: [["Ben Series 0 Book 0", "Ben Series 0 Book 1"], ["Ben Series 1 Book 0"], "Ben Book 4"],
    },
]);

// $concatArrays dotted field.
assert(coll.drop());
assert.commandWorked(
    coll.insert([
        {_id: 1, a: {b: [1, 2, 3]}},
        {_id: 2, a: {b: [4, 5, 6]}},
        {_id: 3, a: {b: [7, 8, 9]}},
    ]),
);
result = coll.aggregate([{$sort: {_id: 1}}, {$group: {_id: null, nums: {$concatArrays: "$a.b"}}}]).toArray();
assert.eq(result, [{_id: null, nums: [1, 2, 3, 4, 5, 6, 7, 8, 9]}]);
assert(coll.drop());

// $concatArrays dotted field, array halfway on path.
assert(coll.drop());
assert.commandWorked(
    coll.insert([
        {_id: 1, a: [{b: [1, 2, 3]}, {b: [4, 5, 6]}]},
        {_id: 2, a: [{b: [7, 8, 9]}, {b: [10, 11, 12]}]},
        {_id: 3, a: [{b: [7, 8, 9]}]},
    ]),
);
result = coll.aggregate([{$sort: {_id: 1}}, {$group: {_id: null, nums: {$concatArrays: "$a.b"}}}]).toArray();
assert.eq(result, [
    {
        _id: null,
        nums: [
            [1, 2, 3],
            [4, 5, 6],
            [7, 8, 9],
            [10, 11, 12],
            [7, 8, 9],
        ],
    },
]);
assert(coll.drop());

// Basic correctness test for $concatArrays used in $bucket (see bucketAuto_concatArrays.js for
// $bucketAuto tests). Though $bucket and $bucketAuto use accumulators in the same way that $group
// does, the test below verifies that everything works properly with serialization and reporting
// results.
assert(coll.drop());
const docs = [];
for (let i = 0; i < 10; i++) {
    docs.push({_id: i, arr: [i]});
}
coll.insertMany(docs);

result = coll
    .aggregate([
        {$sort: {_id: 1}},
        {
            $bucket: {
                groupBy: "$_id",
                boundaries: [0, 5, 10],
                output: {nums: {$concatArrays: "$arr"}},
            },
        },
    ])
    .toArray();
assert.eq(result, [
    {"_id": 0, "nums": [0, 1, 2, 3, 4]},
    {"_id": 5, "nums": [5, 6, 7, 8, 9]},
]);
assert(coll.drop());