Yii2 mongodb分组查询

        $data = MongoDbModelName::getCollection()->aggregate([['$group' => ['_id' => '$user_id', //通过user_id分组去重'total' => ['$sum' => 1]],],['$match' => ['total' => ['$gt' => 1]]]],['allowDiskUse' => true]);

相当于

select user_id,count(1) as total from MongoDbCollection group by user_id having count(1) > 1

aggregate的第二个参数['allowDiskUse' => true]，是表示允许使用内存，比如数据量大的时候，可以加上这个；如果数据量小的话，这个参数可以直接去掉。 如果需要按两个字段进行分组的话，可以将 $group 的_id指定为数组，如下：

$data = MongoDbModelName::getCollection()->aggregate([['$group' => ['_id' => ["aid":"$aid","user_id":"$user_id"],  //通过aid和user_id分组'total' => ['$sum' => 1]],],['$match' => ['total' => ['$gt' => 1]]]],['allowDiskUse' => true]);

相当于

select aid,user_id,count(1) as total from MongoDbCollection group by aid,user_id having count(1) > 1

如果要限制输出条数。可以在aggregate的第一个参数数组尾部中增加["$limit" => 1]，必须是尾部，因为aggregate的会使用第一个参数的元素进行过滤，第一个元素过滤后的结果会给第二个元素，依次内推；实例如下

$data = MongoDbModelName::getCollection()->aggregate([['$group' => ['_id' => ["aid":"$aid","user_id":"$user_id"],  //通过aid和user_id分组'total' => ['$sum' => 1]],],['$match' => ['total' => ['$gt' => 1]]],['$limite' => 15]],['allowDiskUse' => true]);