CODEWITHSUNDEEP
pythonmongodb
knusperwurst
knusperwurst

Reputation: 155

Python with MongoDB - count() function only works with empty search?

i have a strange problem with my python script. I need to get a totalnumber of database entrys in my MongoDB

>>> a = _chatlog.find()
>>> a.count()
4120

Works just like i planned, yay

Now things get strange:

>>> b = _chatlog.find({ "$query": {}, "$orderby": { "_id" : -1 }})
>>> b.count()
0

I perform this Query because i need all entrys in descending order. First i expected a empty cursor but its not:

for data in b:
c += 1

>>> c
4120

How do i get the count method to work properly when i perform querys?

Upvotes: 1

Views: 432

Answers (2)

A. Jesse Jiryu Davis
A. Jesse Jiryu Davis

Reputation: 24007

Count and sort are not compatible. (Nor is it meaningful to combine a sort order with a count.) Remove the $orderby from your query.

Note that if you use the sort method instead of including $orderby, count will work as expected:

collection.find().sort([('_id', -1)]).count()

This works because count simply ignores the sort order. I reiterate that it's meaningless to combine sorting and counting.

Upvotes: 2

metalcharms
metalcharms

Reputation: 56

I can't tell you why query modifiers aren't working but they aren't working for me either. Are you using an older version of Mongo?

Is it possible for you to use ".sort()" instead?

From:

b = _chatlog.find({ "$query": {}, "$orderby": { "_id" : -1 }}).count()

To:

b = _chatlog.find({}).sort({_id:-1}).count()

Upvotes: 0

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