python - 在数组 PyMongo 中查找子文档
问题描述
我想查询任何用户在“2020-03-15”和“2020-04-25”之间对机器学习书发表了哪些评论,将评论从最近到最近排序。
这是我的文件。
lib_books = db.lib_books
document_book1 = ({
"bookid" : "99051fe9-6a9c-46c2-b949-38ef78858dd0",
"title" : "Machine learning",
"author" : "Tom Michael",
"date_of_first_publication" : "2000-10-02",
"number_of_pages" : 414,
"publisher" : "New York : McGraw-Hill",
"topics" : ["Machine learning", "Computer algorithms"],
"checkout_list" : [
{
"time_checked_out" : "2020-03-20 09:11:22",
"userid" : "ef1234",
"comments" : [
{
"comment1" : "I just finished it and it is worth learning!",
"time_commented" : "2020-04-01 10:35:13"
},
{
"comment2" : "Some cases are a little bit outdated.",
"time_commented" : "2020-03-25 13:19:13"
},
{
"comment3" : "Can't wait to learning it!!!",
"time_commented" : "2020-03-21 08:21:42"
}]
},
{
"time_checked_out" : "2020-03-04 16:18:02",
"userid" : "ab1234",
"comments" : [
{
"comment1" : "The book is a little bit difficult but worth reading.",
"time_commented" : "2020-03-20 12:18:02"
},
{
"comment2" : "It's hard and takes a lot of time to understand",
"time_commented" : "2020-03-15 11:22:42"
},
{
"comment3" : "I just start reading, the principle of model is well explained.",
"time_commented" : "2020-03-05 09:11:42"
}]
}]
})
我试过这段代码,但它什么也没返回。
query_test = lib_books.find({"bookid": "99051fe9-6a9c-46c2-b949-38ef78858dd0", "checkout_list.comments.time_commented" : {"$gte" : "2020-03-20", "$lte" : "2020-04-20"}})
for x in query_test:
print(x)
解决方案
你能试试这个
pipeline = [{'$match':{'bookid':"99051fe9-6a9c-46c2-b949-38ef78858dd0"}},//bookid filter
{'$unwind':'$checkout_list'},
{'$unwind':'$checkout_list.comments'},
{'$match':{'checkout_list.comments.time_commented':{"$gte" : "2020-03-20", "$lte" : "2020-04-20"}}},
{'$project':{'_id':0,'bookid':1,'title':1,'comment':'$checkout_list.comments'}},
{'$sort':{'checkout_list.comments.time_commented':-1}}]
query_test = lib_books.aggregate(pipeline)
#{"bookid": "99051fe9-6a9c-46c2-b949-38ef78858dd0", "checkout_list.comments.time_commented" : {"$gte" : "2020-03-20", "$lte" : "2020-04-20"}})
for x in query_test:
print(x)
我建议您将评论字段保留为一个名称,而不是将其保留为“comment1”、“comment2”等。如果该字段是“comment”,则可以将其带到根目录本身
聚合可以修改如下
pipeline = [{'$match':{'bookid':"99051fe9-6a9c-46c2-b949-38ef78858dd0"}},//bookid filter
{'$unwind':'$checkout_list'},
{'$unwind':'$checkout_list.comments'},
{'$match':{'checkout_list.comments.time_commented':{"$gte" : "2020-03-20", "$lte" : "2020-04-20"}}},
{'$project':{'_id':0,'bookid':1,'title':1,'comment':'$checkout_list.comments.comment','time_commented':'$checkout_list.comments.time_commented'}},
{'$sort':{'time_commented':-1}}]
MongoDB 查询,以备不时之需
db.books.aggregate([
{$match:{'bookid':"99051fe9-6a9c-46c2-b949-38ef78858dd0"}},//bookid filter
{$unwind:'$checkout_list'},
{$unwind:'$checkout_list.comments'},
{$match:{'checkout_list.comments.time_commented':{"$gte" : "2020-03-20", "$lte" : "2020-04-20"}}},
{$project:{_id:0,bookid:1,title:1,comment:'$checkout_list.comments.comment',time_commented:'$checkout_list.comments.time_commented'}},
{$sort:{'time_commented':-1}}
])
如果需要搜索多个文档,则可以使用$in
条件。
{$match:{'bookid':{$in:["99051fe9-6a9c-46c2-b949-38ef78858dd0","99051fe9-6a9c-46c2-b949-38ef78858dd1"]}}},//bookid filter
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