使用map-reduce / aggregation的MongoDB查詢？

Question

我在mongo集合中有簡單的數據，它看起來像：

{
"_id" : ObjectId("52b73b1318a7be441dbf36b6"),
"nme" : "Vinod Kumar",
"unm" : "vkumar",
"cat" : ISODate("2013-12-22T19:18:43.873Z"),
"act" : [{
    "nme" : "test activity one",
    "dec" : "This is only about test activity",
    "gat" : ISODate("2013-12-25T19:17:00.873Z"),
    "cat" : ISODate("2013-12-22T19:18:43.873Z")
    }]
},

{
"_id" : ObjectId("52b73b1318a7be441dbf36b6"),
"nme" : "Manoj Kumar",
"unm" : "mkumar",
"cat" : ISODate("2013-12-22T19:18:43.873Z"),
"act" : [{
    "nme" : "test activity three",
    "dec" : "This is only about test activity",
    "gat" : ISODate("2013-12-25T19:17:00.873Z"),
    "cat" : ISODate("2013-12-20T19:18:43.873Z")
    },
        {
    "nme" : "test activity two",
    "dec" : "This is only about test activity",
    "gat" : ISODate("2013-12-25T19:17:00.873Z"),
    "cat" : ISODate("2013-12-21T19:18:43.873Z")
    }]
}

我想按（創建時間）和（unm）用戶名來獲取所有的act（活動）訂單。我還想添加分頁功能，所以我也需要查詢中的限制和偏移量。最后，我期望輸出：

        {
    "nme" : "test activity one",
    "dec" : "This is only about test activity",
    "gat" : ISODate("2013-12-25T19:17:00.873Z"),
    "cat" : ISODate("2013-12-22T19:18:43.873Z"),
    "unm" : "vkumar",
    },
        {
    "nme" : "test activity two",
    "dec" : "This is only about test activity",
    "gat" : ISODate("2013-12-25T19:17:00.873Z"),
    "cat" : ISODate("2013-12-21T19:18:43.873Z"),
    "unm" : "mkumar",
    },
        {
    "nme" : "test activity three",
    "dec" : "This is only about test activity",
    "gat" : ISODate("2013-12-25T19:17:00.873Z"),
    "cat" : ISODate("2013-12-20T19:18:43.873Z"),
    "unm" : "mkumar",
    }

我有200000條記錄在這個集合中。 誰能在不建議單獨創建活動集合的情況下幫助我。

如果有的話，有沒有使用聚合框架的解決方法，我該怎么辦？ 因為我需要使用排序，跳過和限制，所以我不知道如何以最佳性能進行聚合。

我嘗試了map reduce，但是這樣做沒有幫助，因為map reduce將為每個查詢生成靜態結果，並且使用分頁（限制，跳過）時，使用應用程序的多個用戶可能會在結果中發生沖突。

任何幫助或建議，將不勝感激。

謝謝

這是我當前的查詢

$m = new MongoClient();
$c = $m->selectDB("test")->selectCollection("users");

$ops = array(
array(
    '$project' => array(
        "unm" => 1,
        "act" => 1
    )
),
array('$sort' => array('act.cat' => -1 )),
array('$limit' => 10),

);
$results = $c->aggregate($ops);

Answer 1

這是我自己的問題的答案。 我現在意識到mongo具有隱藏的力量：P

$m = new MongoClient();
$c = $m->selectDB("test")->selectCollection("users");

$ops = array(
array(
'$project' => array(
"unm" => 1,
"act" => 1
)
),
array('$unwind' => '$act'),
array('$match' => array('act.sta' => 1)), // if you want some extra queries. In my case I am checking if status of activity is 1
array('$sort' => array('act.cat' => -1 )), // sort by created time
array('$skip' => $page), // skip int variable
array('$limit' =>$config['per_page']), // limit int variable
);

$results = $c->aggregate($ops); 
print_r($results);