如何在聚合MongoDB中进行匹配组？

Question

如果我写匹配和组，就没有工作。如果我删除组或与之相匹配的正常工作

$collection = Yii::$app->mongodb->getCollection('products'); 
      $result = $collection->aggregate(array(
       array(
        '$group' => array(
        '_id' => array('city_id' => '$city_id'), 
        'count' => array('$sum' => 1) 
       ), 
       ), 
       array(
        '$match' => array('user_id' => $filter['user_id']), 
       ), 
       array(
        '$limit' => 20 
       ) 
      ) 
      ); 

Answer 1

我解决了它，当我把比赛组之前，和它的作品对我的作品。

$collection = Yii::$app->mongodb->getCollection('products'); 
      $result = $collection->aggregate(array(
       array(
        '$match' => array('user_id' => $filter['user_id']), 
       ), 
       array(
        '$group' => array(
        '_id' => array('city_id' => '$city_id'), 
        'count' => array('$sum' => 1) 
       ), 
       ), 
       array(
        '$limit' => 20 
       ) 
      ) 
      );