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mongodb $exists always returning 0

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

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

If I run the query (Using pymongo):

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

Works fine. Now:

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

Again works fine. BUT if I try:

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

It returns 0 even though there are 3 records.

like image 384
Amitash Avatar asked Sep 13 '12 02:09

Amitash


2 Answers

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}})
like image 151
JohnnyHK Avatar answered Sep 23 '22 18:09

JohnnyHK


Try the dot syntax:

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

But also see my comment above. You can't have the same key more than once in a (sub-)document.

like image 32
Thomas Avatar answered Sep 19 '22 18:09

Thomas