如何使用Pymongo查詢MongoDB並按月分組結果？

Question

我已經編寫了以下代碼，該代碼正確地按月份編號列出了我的地址集合並帶有計數，但這些是總數，因此我需要有效地添加一個條件，該條件只能返回“類型=綠色”的結果。 我無法解決如何僅在符合這些條件時進行計數。

result = db.address.aggregate([{"$group":{"_id": { "$month": "$date" },
                       "count":{"$sum":1} } } ])

list_of_months = ["nothing", "January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"]

result_sorted = sorted(result, key=lambda x: x['_id'], reverse=False)
for res in result_sorted:
    print(list_of_months[res['_id']], ": ", res['count'])

Answer 1

使用$ match ：

result = db.address.aggregate([{"$match": {"type": "green"}},
                               {"$group": {"_id": {"$month": "$date"},
                                           "count": {"$sum": 1}}}])