'Collection' object is not callable. If you meant to call the 'mapReduce' method on a 'Collection' object it is failing because no such method exists

Question

I'm using pyMongo 1.11 and MongoDB 1.8.2. I'm trying to do a fairly complex Map/Reduce. I prototyped the functions in Mongo and got it working, but when I tried transferring it to Python, I get:

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
/Developer/R-and-D/<ipython-input-71-3c3a43221538> in <module>()
----> 1 results = db.user_actions.mapReduce(map, reduce, "user_entities_interactions")

/Library/Python/2.7/site-packages/pymongo/collection.pyc in __call__(self, *args, **kwargs)
   1099                         "call the '%s' method on a 'Collection' object it is "
   1100                         "failing because no such method exists." %
-> 1101                         self.__name.split(".")[-1])

TypeError: 'Collection' object is not callable. If you meant to call the 'mapReduce' method on a 'Collection' object it is failing because no such method exists.

My collection looks like this:

{ "_id" : ObjectId("..."), "entity_id" : 1556, "user_id" : 466112 }
{ "_id" : ObjectId("..."), "entity_id" : 1366, "user_id" : 10057 }
{ "_id" : ObjectId("..."), "entity_id" : 234, "user_id" : 43650 }
{ "_id" : ObjectId("..."), "entity_id" : 6, "user_id" : 34430 }
{ "_id" : ObjectId("..."), "entity_id" : 461, "user_id" : 3416 }
{ "_id" : ObjectId("..."), "entity_id" : 994, "user_id" : 10057 }
{ "_id" : ObjectId("..."), "entity_id" : 296, "user_id" : 466112 }

The code I'm running in Python is:

map = Code("""function () {
        emit(this.user_id, { 
            user_id : this.user_id,
            entity_id : this.entity_id});
    }""")

reduce = Code("""function (key, values) {
        var entities = { user_id : values[0].user_id, entity_id : [ ] };
        for (var i = 0; i < values.length; i++) {
            entities.entity_id[i] = values[i].entity_id;
        }
        return entities;
    }""")
results = db.user_actions.mapReduce(map, reduce, "user_entities_interactions")

What the result should look like is:

{ "_id" : 3416, "value" : { "user_id" : 3416, "entity_id" : 461 } }
{ "_id" : 10057, "value" : { "user_id" : 10057, "entity_id" : [ 1366, 994 ] } }
{ "_id" : 34430, "value" : { "user_id" : 34430, "entity_id" : 6 } }
{ "_id" : 43650, "value" : { "user_id" : 43650, "entity_id" : 234 } }
{ "_id" : 466112, "value" : { "user_id" : 466112, "entity_id" : [ 1556, 296 ] } }

I'm not clear on what the problem is. The error says that the 'Collection' object has no mapReduce method, but that's clearly not true as the example at http://api.mongodb.org/python/current/examples/map_reduce.html works and what is 'things' if not a collection?

Also, in case you're wondering why I'm not doing this with group() it's because I have more than 20000 unique keys.

Answer 1

It's not called mapReduce, but map_reduce. Try:

results = db.user_actions.map_reduce(map, reduce, "user_entities_interactions")