/*
  Run all the aggregation tests
*/

/* load the test documents */
load('jstests/aggregation/data/articles.js');

// make sure we're using the right db; this is the same as "use mydb;" in shell
db = db.getSiblingDB("aggdb");

// just passing through fields
var p1 = db.runCommand({aggregate: "article", pipeline: [{$project: {tags: 1, pageViews: 1}}]});

var p1result = [
    {"_id": 1, "pageViews": 5, "tags": ["fun", "good", "fun"]},
    {"_id": 2, "pageViews": 7, "tags": ["fun", "nasty"]},
    {"_id": 3, "pageViews": 6, "tags": ["nasty", "filthy"]}
];

assert.docEq(p1.result, p1result, 'p1 failed');

// a simple array unwinding
var u1 = db.runCommand({aggregate: "article", pipeline: [{$unwind: "$tags"}]});

var u1result = [
    {
      "_id": 1,
      "title": "this is my title",
      "author": "bob",
      "posted": ISODate("2004-03-21T18:59:54Z"),
      "pageViews": 5,
      "tags": "fun",
      "comments":
          [{"author": "joe", "text": "this is cool"}, {"author": "sam", "text": "this is bad"}],
      "other": {"foo": 5}
    },
    {
      "_id": 1,
      "title": "this is my title",
      "author": "bob",
      "posted": ISODate("2004-03-21T18:59:54Z"),
      "pageViews": 5,
      "tags": "good",
      "comments":
          [{"author": "joe", "text": "this is cool"}, {"author": "sam", "text": "this is bad"}],
      "other": {"foo": 5}
    },
    {
      "_id": 1,
      "title": "this is my title",
      "author": "bob",
      "posted": ISODate("2004-03-21T18:59:54Z"),
      "pageViews": 5,
      "tags": "fun",
      "comments":
          [{"author": "joe", "text": "this is cool"}, {"author": "sam", "text": "this is bad"}],
      "other": {"foo": 5}
    },
    {
      "_id": 2,
      "title": "this is your title",
      "author": "dave",
      "posted": ISODate("2030-08-08T04:11:10Z"),
      "pageViews": 7,
      "tags": "fun",
      "comments": [
          {"author": "barbara", "text": "this is interesting"},
          {"author": "jenny", "text": "i like to play pinball", "votes": 10}
      ],
      "other": {"bar": 14}
    },
    {
      "_id": 2,
      "title": "this is your title",
      "author": "dave",
      "posted": ISODate("2030-08-08T04:11:10Z"),
      "pageViews": 7,
      "tags": "nasty",
      "comments": [
          {"author": "barbara", "text": "this is interesting"},
          {"author": "jenny", "text": "i like to play pinball", "votes": 10}
      ],
      "other": {"bar": 14}
    },
    {
      "_id": 3,
      "title": "this is some other title",
      "author": "jane",
      "posted": ISODate("2000-12-31T05:17:14Z"),
      "pageViews": 6,
      "tags": "nasty",
      "comments": [
          {"author": "will", "text": "i don't like the color"},
          {"author": "jenny", "text": "can i get that in green?"}
      ],
      "other": {"bar": 14}
    },
    {
      "_id": 3,
      "title": "this is some other title",
      "author": "jane",
      "posted": ISODate("2000-12-31T05:17:14Z"),
      "pageViews": 6,
      "tags": "filthy",
      "comments": [
          {"author": "will", "text": "i don't like the color"},
          {"author": "jenny", "text": "can i get that in green?"}
      ],
      "other": {"bar": 14}
    }
];

assert.docEq(u1.result, u1result, 'u1 failed');

// unwind an array at the end of a dotted path
db.ut.drop();
db.ut.save({_id: 4, a: 1, b: {e: 7, f: [4, 3, 2, 1]}, c: 12, d: 17});
var u2 = db.runCommand({aggregate: "ut", pipeline: [{$unwind: "$b.f"}]});

var u2result = [
    {"_id": 4, "a": 1, "b": {"e": 7, "f": 4}, "c": 12, "d": 17},
    {"_id": 4, "a": 1, "b": {"e": 7, "f": 3}, "c": 12, "d": 17},
    {"_id": 4, "a": 1, "b": {"e": 7, "f": 2}, "c": 12, "d": 17},
    {"_id": 4, "a": 1, "b": {"e": 7, "f": 1}, "c": 12, "d": 17}
];

assert.docEq(u2.result, u2result, 'u2 failed');

// combining a projection with unwinding an array
var p2 = db.runCommand({
    aggregate: "article",
    pipeline: [{$project: {author: 1, tags: 1, pageViews: 1}}, {$unwind: "$tags"}]
});

var p2result = [
    {"_id": 1, "author": "bob", "pageViews": 5, "tags": "fun"},
    {"_id": 1, "author": "bob", "pageViews": 5, "tags": "good"},
    {"_id": 1, "author": "bob", "pageViews": 5, "tags": "fun"},
    {"_id": 2, "author": "dave", "pageViews": 7, "tags": "fun"},
    {"_id": 2, "author": "dave", "pageViews": 7, "tags": "nasty"},
    {"_id": 3, "author": "jane", "pageViews": 6, "tags": "nasty"},
    {"_id": 3, "author": "jane", "pageViews": 6, "tags": "filthy"}
];

assert.docEq(p2.result, p2result, 'p2 failed');

// pulling values out of subdocuments
var p3 = db.runCommand({
    aggregate: "article",
    pipeline: [{$project: {otherfoo: "$other.foo", otherbar: "$other.bar"}}]
});

var p3result = [{"_id": 1, "otherfoo": 5}, {"_id": 2, "otherbar": 14}, {"_id": 3, "otherbar": 14}];

assert.docEq(p3.result, p3result, 'p3 failed');

// projection includes a computed value
var p4 = db.runCommand({
    aggregate: "article",
    pipeline: [{$project: {author: 1, daveWroteIt: {$eq: ["$author", "dave"]}}}]
});

var p4result = [
    {"_id": 1, "author": "bob", "daveWroteIt": false},
    {"_id": 2, "author": "dave", "daveWroteIt": true},
    {"_id": 3, "author": "jane", "daveWroteIt": false}
];

assert.docEq(p4.result, p4result, 'p4 failed');

// projection includes a virtual (fabricated) document
var p5 = db.runCommand({
    aggregate: "article",
    pipeline: [
        {$project: {author: 1, pageViews: 1, tags: 1}},
        {$unwind: "$tags"},
        {$project: {author: 1, subDocument: {foo: "$pageViews", bar: "$tags"}}}
    ]
});

var p5result = [
    {"_id": 1, "author": "bob", "subDocument": {"foo": 5, "bar": "fun"}},
    {"_id": 1, "author": "bob", "subDocument": {"foo": 5, "bar": "good"}},
    {"_id": 1, "author": "bob", "subDocument": {"foo": 5, "bar": "fun"}},
    {"_id": 2, "author": "dave", "subDocument": {"foo": 7, "bar": "fun"}},
    {"_id": 2, "author": "dave", "subDocument": {"foo": 7, "bar": "nasty"}},
    {"_id": 3, "author": "jane", "subDocument": {"foo": 6, "bar": "nasty"}},
    {"_id": 3, "author": "jane", "subDocument": {"foo": 6, "bar": "filthy"}}
];

assert.docEq(p5.result, p5result, 'p5 failed');

// multi-step aggregate
// nested expressions in computed fields
var p6 = db.runCommand({
    aggregate: "article",
    pipeline: [
        {$project: {author: 1, tags: 1, pageViews: 1}},
        {$unwind: "$tags"},
        {
          $project: {
              author: 1,
              tag: "$tags",
              pageViews: 1,
              daveWroteIt: {$eq: ["$author", "dave"]},
              weLikeIt: {$or: [{$eq: ["$author", "dave"]}, {$eq: ["$tags", "good"]}]}
          }
        }
    ]
});

var p6result = [
    {
      "_id": 1,
      "author": "bob",
      "pageViews": 5,
      "tag": "fun",
      "daveWroteIt": false,
      "weLikeIt": false
    },
    {
      "_id": 1,
      "author": "bob",
      "pageViews": 5,
      "tag": "good",
      "daveWroteIt": false,
      "weLikeIt": true
    },
    {
      "_id": 1,
      "author": "bob",
      "pageViews": 5,
      "tag": "fun",
      "daveWroteIt": false,
      "weLikeIt": false
    },
    {
      "_id": 2,
      "author": "dave",
      "pageViews": 7,
      "tag": "fun",
      "daveWroteIt": true,
      "weLikeIt": true
    },
    {
      "_id": 2,
      "author": "dave",
      "pageViews": 7,
      "tag": "nasty",
      "daveWroteIt": true,
      "weLikeIt": true
    },
    {
      "_id": 3,
      "author": "jane",
      "pageViews": 6,
      "tag": "nasty",
      "daveWroteIt": false,
      "weLikeIt": false
    },
    {
      "_id": 3,
      "author": "jane",
      "pageViews": 6,
      "tag": "filthy",
      "daveWroteIt": false,
      "weLikeIt": false
    }
];

assert.docEq(p6.result, p6result, 'p6 failed');

// slightly more complex computed expression; $ifNull
var p7 = db.runCommand({
    aggregate: "article",
    pipeline:
        [{$project: {theSum: {$add: ["$pageViews", {$ifNull: ["$other.foo", "$other.bar"]}]}}}]
});

var p7result = [{"_id": 1, "theSum": 10}, {"_id": 2, "theSum": 21}, {"_id": 3, "theSum": 20}];

assert.docEq(p7.result, p7result, 'p7 failed');

// dotted path inclusion; _id exclusion
var p8 = db.runCommand({
    aggregate: "article",
    pipeline:
        [{$project: {_id: 0, author: 1, tags: 1, "comments.author": 1}}, {$unwind: "$tags"}]
});

var p8result = [
    {"author": "bob", "tags": "fun", "comments": [{"author": "joe"}, {"author": "sam"}]},
    {"author": "bob", "tags": "good", "comments": [{"author": "joe"}, {"author": "sam"}]},
    {"author": "bob", "tags": "fun", "comments": [{"author": "joe"}, {"author": "sam"}]},
    {"author": "dave", "tags": "fun", "comments": [{"author": "barbara"}, {"author": "jenny"}]},
    {"author": "dave", "tags": "nasty", "comments": [{"author": "barbara"}, {"author": "jenny"}]},
    {"author": "jane", "tags": "nasty", "comments": [{"author": "will"}, {"author": "jenny"}]},
    {"author": "jane", "tags": "filthy", "comments": [{"author": "will"}, {"author": "jenny"}]}
];

assert.docEq(p8.result, p8result, 'p8 failed');

// collapse a dotted path with an intervening array
var p9 = db.runCommand({
    aggregate: "article",
    pipeline: [{$project: {_id: 0, author: 1, commentsAuthor: "$comments.author"}}]
});

var p9result = [
    {"author": "bob", "commentsAuthor": ["joe", "sam"]},
    {"author": "dave", "commentsAuthor": ["barbara", "jenny"]},
    {"author": "jane", "commentsAuthor": ["will", "jenny"]}
];

assert.docEq(p9.result, p9result, 'p9 failed');

// simple sort
var p10 = db.runCommand({aggregate: "article", pipeline: [{$sort: {title: 1}}]});

var p10result = [
    {
      "_id": 1,
      "title": "this is my title",
      "author": "bob",
      "posted": ISODate("2004-03-21T18:59:54Z"),
      "pageViews": 5,
      "tags": ["fun", "good", "fun"],
      "comments":
          [{"author": "joe", "text": "this is cool"}, {"author": "sam", "text": "this is bad"}],
      "other": {"foo": 5}
    },
    {
      "_id": 3,
      "title": "this is some other title",
      "author": "jane",
      "posted": ISODate("2000-12-31T05:17:14Z"),
      "pageViews": 6,
      "tags": ["nasty", "filthy"],
      "comments": [
          {"author": "will", "text": "i don't like the color"},
          {"author": "jenny", "text": "can i get that in green?"}
      ],
      "other": {"bar": 14}
    },
    {
      "_id": 2,
      "title": "this is your title",
      "author": "dave",
      "posted": ISODate("2030-08-08T04:11:10Z"),
      "pageViews": 7,
      "tags": ["fun", "nasty"],
      "comments": [
          {"author": "barbara", "text": "this is interesting"},
          {"author": "jenny", "text": "i like to play pinball", "votes": 10}
      ],
      "other": {"bar": 14}
    }
];

assert.docEq(p10.result, p10result, 'p10 failed');

// unwind on nested array
db.p11.drop();
db.p11.save({
    _id: 5,
    name: 'MongoDB',
    items: {authors: ['jay', 'vivek', 'bjornar'], dbg: [17, 42]},
    favorites: ['pickles', 'ice cream', 'kettle chips']
});

var p11 = db.runCommand({
    aggregate: "p11",
    pipeline: [
        {$unwind: "$items.authors"},
        {$project: {name: 1, author: "$items.authors"}},
    ]
});

p11result = [
    {"_id": 5, "name": "MongoDB", "author": "jay"},
    {"_id": 5, "name": "MongoDB", "author": "vivek"},
    {"_id": 5, "name": "MongoDB", "author": "bjornar"}
];

assert.docEq(p11.result, p11result, 'p11 failed');

// multiply test
var p12 = db.runCommand({
    aggregate: "article",
    pipeline: [{
        $project:
            {theProduct: {$multiply: ["$pageViews", {$ifNull: ["$other.foo", "$other.bar"]}]}}
    }]
});

var p12result =
    [{"_id": 1, "theProduct": 25}, {"_id": 2, "theProduct": 98}, {"_id": 3, "theProduct": 84}];

assert.docEq(p12.result, p12result, 'p12 failed');

// subtraction test
var p13 = db.runCommand({
    aggregate: "article",
    pipeline: [{
        $project: {
            theDifference:
                {$subtract: ["$pageViews", {$ifNull: ["$other.foo", "$other.bar"]}]}
        }
    }]
});

var p13result = [
    {"_id": 1, "theDifference": 0},
    {"_id": 2, "theDifference": -7},
    {"_id": 3, "theDifference": -8}
];

assert.docEq(p13.result, p13result, 'p13 failed');

// mod test
var p14 = db.runCommand({
    aggregate: "article",
    pipeline: [{
        $project: {
            theRemainder: {
                $mod: [
                    {$ifNull: ["$other.foo", "$other.bar"]},
                    "$pageViews",
                ]
            }
        }
    }]
});

var p14result =
    [{"_id": 1, "theRemainder": 0}, {"_id": 2, "theRemainder": 0}, {"_id": 3, "theRemainder": 2}];

assert.docEq(p14.result, p14result, 'p14 failed');

// toUpper test
var p15 = db.runCommand(
    {aggregate: "article", pipeline: [{$project: {author: {$toUpper: "$author"}, pageViews: 1}}]});

var p15result = [
    {"_id": 1, "author": "BOB", "pageViews": 5},
    {"_id": 2, "author": "DAVE", "pageViews": 7},
    {"_id": 3, "author": "JANE", "pageViews": 6}
];

assert.docEq(p15.result, p15result, 'p15 failed');

// toLower test
var p16 = db.runCommand({
    aggregate: "article",
    pipeline: [
        {$project: {author: {$toUpper: "$author"}, pageViews: 1}},
        {$project: {author: {$toLower: "$author"}, pageViews: 1}}
    ]
});

var p16result = [
    {
      "_id": 1,
      "author": "bob",
      "pageViews": 5,
    },
    {
      "_id": 2,
      "author": "dave",
      "pageViews": 7,
    },
    {
      "_id": 3,
      "author": "jane",
      "pageViews": 6,
    }
];

assert.docEq(p16.result, p16result, 'p16 failed');

// substr test
var p17 = db.runCommand({
    aggregate: "article",
    pipeline: [{
        $project: {
            author: {$substrBytes: ["$author", 1, 2]},
        }
    }]
});

var p17result =
    [{"_id": 1, "author": "ob"}, {"_id": 2, "author": "av"}, {"_id": 3, "author": "an"}];

assert.docEq(p17.result, p17result, 'p17 failed');

// strcasecmp test
var p18 = db.runCommand({
    aggregate: "article",
    pipeline: [{
        $project: {
            tags: 1,
            thisisalametest: {$strcasecmp: ["foo", "bar"]},
            thisisalamepass: {$strcasecmp: ["foo", "foo"]}
        }
    }]
});

var p18result = [
    {"_id": 1, "tags": ["fun", "good", "fun"], "thisisalametest": 1, "thisisalamepass": 0},
    {"_id": 2, "tags": ["fun", "nasty"], "thisisalametest": 1, "thisisalamepass": 0},
    {"_id": 3, "tags": ["nasty", "filthy"], "thisisalametest": 1, "thisisalamepass": 0}
];

assert.docEq(p18.result, p18result, 'p18 failed');

// date tests
var p19 = db.runCommand({
    aggregate: "article",
    pipeline: [{
        $project: {
            authors: 1,
            posted: 1,
            seconds: {$second: "$posted"},
            minutes: {$minute: "$posted"},
            hour: {$hour: "$posted"},
            dayOfYear: {$dayOfYear: "$posted"},
            dayOfMonth: {$dayOfMonth: "$posted"},
            dayOfWeek: {$dayOfWeek: "$posted"},
            month: {$month: "$posted"},
            week: {$week: "$posted"},
            year: {$year: "$posted"}
        }
    }]
});

var p19result = [
    {
      "_id": 1,
      "posted": ISODate("2004-03-21T18:59:54Z"),
      "seconds": 54,
      "minutes": 59,
      "hour": 18,
      "dayOfYear": 81,
      "dayOfMonth": 21,
      "dayOfWeek": 1,
      "month": 3,
      "week": 12,
      "year": 2004,
    },
    {
      "_id": 2,
      "posted": ISODate("2030-08-08T04:11:10Z"),
      "seconds": 10,
      "minutes": 11,
      "hour": 4,
      "dayOfYear": 220,
      "dayOfMonth": 8,
      "dayOfWeek": 5,
      "month": 8,
      "week": 31,
      "year": 2030,
    },
    {
      "_id": 3,
      "posted": ISODate("2000-12-31T05:17:14Z"),
      "seconds": 14,
      "minutes": 17,
      "hour": 5,
      "dayOfYear": 366,
      "dayOfMonth": 31,
      "dayOfWeek": 1,
      "month": 12,
      "week": 53,
      "year": 2000,
    }
];

assert.docEq(p19.result, p19result, 'p19 failed');

db.vartype.drop();
db.vartype.save({x: 17, y: "foo"});

// ternary conditional operator
var p21 = db.runCommand({
    aggregate: "article",
    pipeline: [{
        $project: {
            _id: 0,
            author: 1,
            pageViews: {
                $cond:
                    [{$eq: ["$author", "dave"]}, {$add: ["$pageViews", 1000]}, "$pageViews"]
            }
        }
    }]
});

var p21result = [
    {"author": "bob", "pageViews": 5},
    {"author": "dave", "pageViews": 1007},
    {"author": "jane", "pageViews": 6}
];

assert.docEq(p21.result, p21result, 'p21 failed');

// simple matching
var m1 = db.runCommand({aggregate: "article", pipeline: [{$match: {author: "dave"}}]});

var m1result = [{
    "_id": 2,
    "title": "this is your title",
    "author": "dave",
    "posted": ISODate("2030-08-08T04:11:10Z"),
    "pageViews": 7,
    "tags": ["fun", "nasty"],
    "comments": [
        {"author": "barbara", "text": "this is interesting"},
        {"author": "jenny", "text": "i like to play pinball", "votes": 10}
    ],
    "other": {"bar": 14}
}];

assert.docEq(m1.result, m1result, 'm1 failed');

// combining matching with a projection
var m2 = db.runCommand({
    aggregate: "article",
    pipeline: [
        {$project: {title: 1, author: 1, pageViews: 1, tags: 1, comments: 1}},
        {$unwind: "$tags"},
        {$match: {tags: "nasty"}}
    ]
});

var m2result = [
    {
      "_id": 2,
      "title": "this is your title",
      "author": "dave",
      "pageViews": 7,
      "tags": "nasty",
      "comments": [
          {"author": "barbara", "text": "this is interesting"},
          {"author": "jenny", "text": "i like to play pinball", "votes": 10}
      ]
    },
    {
      "_id": 3,
      "title": "this is some other title",
      "author": "jane",
      "pageViews": 6,
      "tags": "nasty",
      "comments": [
          {"author": "will", "text": "i don't like the color"},
          {"author": "jenny", "text": "can i get that in green?"}
      ]
    }
];

assert.docEq(m2.result, m2result, 'm2 failed');

// group by tag, _id is a field reference
var g1 = db.runCommand({
    aggregate: "article",
    pipeline: [
        {$project: {author: 1, tags: 1, pageViews: 1}},
        {$unwind: "$tags"},
        {$group: {_id: "$tags", docsByTag: {$sum: 1}, viewsByTag: {$sum: "$pageViews"}}},
        {$sort: {'_id': 1}}
    ]
});

var g1result = [
    {"_id": "filthy", "docsByTag": 1, "viewsByTag": 6},
    {"_id": "fun", "docsByTag": 3, "viewsByTag": 17},
    {"_id": "good", "docsByTag": 1, "viewsByTag": 5},
    {"_id": "nasty", "docsByTag": 2, "viewsByTag": 13},
];

assert.docEq(g1.result, g1result, 'g1 failed');

// $max, and averaging in a final projection; _id is structured
var g2 = db.runCommand({
    aggregate: "article",
    pipeline: [
        {$project: {author: 1, tags: 1, pageViews: 1}},
        {$unwind: "$tags"},
        {
          $group: {
              _id: {tags: "$tags"},
              docsByTag: {$sum: 1},
              viewsByTag: {$sum: "$pageViews"},
              mostViewsByTag: {$max: "$pageViews"},
          }
        },
        {
          $project: {
              _id: false,
              tag: "$_id.tags",
              mostViewsByTag: 1,
              docsByTag: 1,
              viewsByTag: 1,
              avgByTag: {$divide: ["$viewsByTag", "$docsByTag"]}
          }
        },
        {$sort: {'docsByTag': 1, 'viewsByTag': 1}}
    ]
});

var g2result = [
    {"docsByTag": 1, "viewsByTag": 5, "mostViewsByTag": 5, "tag": "good", "avgByTag": 5},
    {"docsByTag": 1, "viewsByTag": 6, "mostViewsByTag": 6, "tag": "filthy", "avgByTag": 6},
    {"docsByTag": 2, "viewsByTag": 13, "mostViewsByTag": 7, "tag": "nasty", "avgByTag": 6.5},
    {
      "docsByTag": 3,
      "viewsByTag": 17,
      "mostViewsByTag": 7,
      "tag": "fun",
      "avgByTag": 5.666666666666667
    }
];

assert.docEq(g2.result, g2result, 'g2 failed');

// $push as an accumulator; can pivot data
var g3 = db.runCommand({
    aggregate: "article",
    pipeline: [
        {
          $project: {
              author: 1,
              tags: 1,
          }
        },
        {$unwind: "$tags"},
        {$group: {_id: {tags: "$tags"}, authors: {$push: "$author"}}},
        {$sort: {'_id': 1}}
    ]
});

var g3result = [
    {"_id": {"tags": "filthy"}, "authors": ["jane"]},
    {"_id": {"tags": "fun"}, "authors": ["bob", "bob", "dave"]},
    {"_id": {"tags": "good"}, "authors": ["bob"]},
    {"_id": {"tags": "nasty"}, "authors": ["dave", "jane"]}
];

assert.docEq(g3.result, g3result, 'g3 failed');

// $avg, and averaging in a final projection
var g4 = db.runCommand({
    aggregate: "article",
    pipeline: [
        {$project: {author: 1, tags: 1, pageViews: 1}},
        {$unwind: "$tags"},
        {
          $group: {
              _id: {tags: "$tags"},
              docsByTag: {$sum: 1},
              viewsByTag: {$sum: "$pageViews"},
              avgByTag: {$avg: "$pageViews"},
          }
        },
        {$sort: {'_id': 1}}
    ]
});

var g4result = [
    {"_id": {"tags": "filthy"}, "docsByTag": 1, "viewsByTag": 6, "avgByTag": 6},
    {"_id": {"tags": "fun"}, "docsByTag": 3, "viewsByTag": 17, "avgByTag": 5.666666666666667},
    {"_id": {"tags": "good"}, "docsByTag": 1, "viewsByTag": 5, "avgByTag": 5},
    {"_id": {"tags": "nasty"}, "docsByTag": 2, "viewsByTag": 13, "avgByTag": 6.5}
];

assert.docEq(g4.result, g4result, 'g4 failed');

// $addToSet as an accumulator; can pivot data
var g5 = db.runCommand({
    aggregate: "article",
    pipeline: [
        {
          $project: {
              author: 1,
              tags: 1,
          }
        },
        {$unwind: "$tags"},
        {$group: {_id: {tags: "$tags"}, authors: {$addToSet: "$author"}}},
        {$sort: {'_id': 1}}
    ]
});

// $addToSet doesn't guarantee order so we shouldn't test for it.
g5.result.forEach(function(obj) {
    obj.authors.sort();
});

var g5result = [
    {"_id": {"tags": "filthy"}, "authors": ["jane"]},
    {
      "_id": {"tags": "fun"},
      "authors": [
          "bob",
          "dave",
      ]
    },
    {"_id": {"tags": "good"}, "authors": ["bob"]},
    {
      "_id": {"tags": "nasty"},
      "authors": [
          "dave",
          "jane",
      ]
    }
];

assert.docEq(g5.result, g5result, 'g5 failed');

// $first and $last accumulators, constant _id
var g6 = db.runCommand({
    aggregate: "article",
    pipeline: [
        {$sort: {author: -1}},
        {
          $group: {
              _id: "authors",                  /* constant string, *not* a field reference */
              firstAuthor: {$last: "$author"}, /* note reverse sort above */
              lastAuthor: {$first: "$author"}, /* note reverse sort above */
              count: {$sum: 1}
          }
        }
    ]
});

var g6result = [{"_id": "authors", firstAuthor: "bob", lastAuthor: "jane", count: 3}];

// Test unwind on an unused field
var g7 = db.runCommand({
    aggregate: "article",
    pipeline: [
        {$unwind: '$tags'},
        {
          $group: {
              _id: "tag_count", /* constant string, *not* a field reference */
              count: {$sum: 1}
          }
        }
    ]
});
assert.eq(g7.result[0].count, 7);