mongodb $ exists总是返回0 [英] mongodb $exists always returning 0

问题描述

我有一个这样的数据库集合(名为fols):

I have a database collection (named fols) like so:

{'followers':
        {
           '123':1
           '123':2
           '123':3
         }
}

如果我运行查询(使用pymongo):

If I run the query (Using pymongo):

cursor = fols.find()
cursor.count()
>>3

工作正常.现在:

cursor = fols.find({'followers':{'123':1}})
cursor.count()
>>1

再次正常工作.但是，如果我尝试:

Again works fine. BUT if I try:

cursor = fols.find({'followers':{'123':{'$exists': True}}})
cursor.count()
>> 0

即使有3条记录，它也会返回0.

It returns 0 even though there are 3 records.

推荐答案

当您不匹配完整的对象时，您需要使用

When you're not matching a complete object you need to use dot notation to use an operator against an embedded object. So in this case:

cursor = fols.find({'followers.123':{'$exists': True}})

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