Question

我有这些文件

 {
"_id": ObjectId("54de59a73674754822a1d71c"),
"date": ISODate("2015-02-13T00:00:00.0Z"),
"code1": "AAA",
"code2": "BBB",
"currency": "€",
"price": 177.6
}   

{
"_id": ObjectId("54de59a73674754822a1d71c"),
"date": ISODate("2015-02-13T00:00:00.0Z"),
"code1": "AAA",
"code2": "BBB",
"currency": "€",
"price": 90.6
}

{
"_id": ObjectId("54de59a73674754822a1d71c"),
"date": ISODate("2015-02-13T00:00:00.0Z"),
"code1": "AAA",
"code2": "BBB",
"currency": "€",
"price": 150.6
}

{
"_id": ObjectId("54de59a73674754822a1d71c"),
"date": ISODate("2015-02-13T00:00:00.0Z"),
"code1": "CCC",
"code2": "DDD",
"currency": "€",
"price": 100.6
}

我希望使用mongodb的聚合框架按code1和code2对文档进行分组，以便： - 计算出现次数，然后 - 使用$ last运算符从组中获得最便宜的。

这是我的代码，它正在根据事件对文档进行排序，但是$ last给了我一个随机文档，而不是组中最便宜的文档。

public function aggregateQuery(){

    $connection=  new \MongoClient('server');
    $dbname = $connection->selectDB('db');
    $collection = $dbname->selectCollection('collection');

    $parameters = array();  
    $match = array('currency' => "€");
    array_push($parameters, array('$match' => $match));

    $group_parameters = array('_id' => array('code1' => '$code1', 'code2' => '$code2'), 'price' => array('$last' =>'$price'), 'occurrences' => array('$sum' => 1));

    array_push($parameters, $array('$group' => group_parameters));
    array_push($parameters,  array('$sort' => array('occurrences' => 1)));

    return $$collection->aggregate($parameters);

}

我想得到的结果是： AAA - BBB：90.6 CCC - DDD：100.6

想法？谢谢！

使用聚合对组中的元素进行排序

0 个答案: