Slow Grouping with MongoDB

本文关键字：MongoDB with Grouping Slow | 更新日期: 2023-09-27

下面的代码按publish_target、type和status对80,000篇文章进行分组，耗时30秒。

是否有明显的方法来改善加载时间?

            //by publish target
            $collection = $this->mongoDB->Post;
            $keys = array('publish_target' => true);
            $initial = array("count" => 0);
            $reduce = "function (obj, prev) { prev.count++; }";
            $result = $collection->group($keys, $initial, $reduce);
            foreach ($result['retval'] as $value) {
                $this->results['Post']['publish_target'][] = array('key' => $value['publish_target'], 'value' => $value['count']);
            }
        // by type
        $collection = $this->mongoDB->Post;
        $keys = array('type' => true);
        $initial = array("count" => 0);
        $reduce = "function (obj, prev) { prev.count++; }";
        $result = $collection->group($keys, $initial, $reduce);
        foreach ($result['retval'] as $value) {
            $this->results['Post']['type'][] = array('key' => $value['type'], 'value' => $value['count']);
        }
        // by status
        $collection = $this->mongoDB->Post;
        $keys = array('status' => true);
        $initial = array("count" => 0);
        $reduce = "function (obj, prev) { prev.count++; }";
        $result = $collection->group($keys, $initial, $reduce);
        foreach ($result['retval'] as $value) {
            $this->results['Post']['status'][] = array('key' => $value['status'], 'value' => $value['count']);
        }

固定

            $ops = array(
                array(
                    '$group' => array(
                        '_id' => array($arrayKey => '$'.$arrayKey),
                        'count' => array('$sum' => 1)
                    )
                )
            );
            $retrieved = $collection->aggregate($ops);

首先，您正在运行的不是单个聚合，而是基于前一个聚合的输出运行三个聚合，并且不清楚为什么要这样做，而不是在单个聚合中按publish_target、type和status分组。

其次，你使用的是通过Javascript实现的group()函数，而不是在服务器上本地运行的Aggregation Framework。您唯一需要的查询/命令是:

db.post.aggregate({$group:{
          _id: { publish_target : "$publish_target" },
          count: {$sum : 1}
} );

现在您将在服务器上获得这些计数。