我的文件看起来像：
_id: 1,
chat: [
{
sender: "michael",
message: "hello",
status: "pending",
receiver: "jennifer"
},
{
sender: "michael",
message: "how are you ?",
status: "sent",
receiver: "jennifer"
}
]
_id: 2,
chat: [
{
sender: "michael",
message: "hello",
status: "pending",
receiver: "bobby"
},
{
sender: "michael",
message: "how are you ?",
status: "pending",
receiver: "bobby"
}
]
如何从嵌入文档中获取status="pending"的计数？我希望结果如下所示：
_id: 1,
sender: "michael",
receiver: "jennifer",
status_pending: 1
_id: 2,
sender: "michael",
receiver: "bobby",
status_pending: 2,
我不知道如何在MongoDB中使用$unstyle、$group、$size。请有人帮我…
您可以首先$un转聊天，然后$group通过id、发送者和接收者并使用$sum计数，然后$project返回最终结果。
db.collection.aggregate([
{$unwind: '$chat'},
{$match: {'chat.status': 'pending'}},
{$group: {
_id: {_id: '$_id', sender: '$chat.sender',receiver: '$chat.receiver'},
status_pending: {$sum: 1}
}},
{$project: {
_id: '$_id._id',
sender: '$_id.sender',
receiver: '$_id.receiver',
status_pending: 1
}}
])
最终结果
[{"status_pending":2,"_id":2,"sender":"michael","receiver":"bobby"},{"status_pending":1,"_id":1,"sender":"michael","receiver":"jennifer"}]
