mongodb 分组如何返回所有字段

[fangwenxue]

[
    {
        "$group": {
            "_id": "$username",
            "total": {"$sum": 1}
        }
    }
]

想实现的是

select count(*) as total, * from table group by username

[namidairo]

```
[
{
$group: {
_id: "$username",
amount: {$sum: 1},
items: {$push: "$$ROOT"}
}
}
]
```
push: https://docs.mongodb.com/manual/reference/operator/aggregation/push/#mongodb-group-grp.-push
$$ROOT: https://docs.mongodb.com/manual/reference/aggregation-variables/#mongodb-variable-variable.ROOT