pymongo mapreduce db assertion failure

I'm just getting started with mongo and map/reduce, and I'm coming into the following error when using pymongo that I don't get when using the mongo command line directly (I realize there is a similar question to this one, but mine seems far more basic).

I'm using the example directly from the pymongo documentation: http://api.mongodb.org/python/1.3%2B/examples/map_reduce.html

from pymongo import Connection
from pymongo.code import Code

db = Connection().map_reduce_example
db.things.insert({"x": 1, "tags": ["dog", "cat"]})
db.things.insert({"x": 2, "tags": ["cat"]})
db.things.insert({"x": 3, "tags": ["mouse", "cat", "dog"]})
db.things.insert({"x": 4, "tags": 开发者_JS百科[]})


m = Code("function () {this.tags.forEach(function(z) {emit('d, 1);});}")
m = Code("function () {emit('dog', 1);}")

r = Code("function (key, values) {var total = 0;for (var i = 0; i < values.length; i++) {total += values[i];}return total;}")


result = db.things.map_reduce(m, r)

This gives me the following error:

Traceback (most recent call last):
  File "demo.py", line 17, in <module>
    result = db.things.map_reduce(m, r)
  File "/usr/local/lib/python2.6/dist-packages/pymongo-1.9-py2.6-linux-i686.egg/pymongo/collection.py", line 943, in map_reduce
    map=map, reduce=reduce, **kwargs)
  File "/usr/local/lib/python2.6/dist-packages/pymongo-1.9-py2.6-linux-i686.egg/pymongo/database.py", line 293, in command
    msg, allowable_errors)
  File "/usr/local/lib/python2.6/dist-packages/pymongo-1.9-py2.6-linux-i686.egg/pymongo/helpers.py", line 119, in _check_command_response
    raise OperationFailure(msg % response["errmsg"])
pymongo.errors.OperationFailure: command SON([('mapreduce', u'things'), ('map', Code("function () {emit('dog', 1);}", {})), ('reduce', Code('function (key, values) {var total = 0;for (var i = 0; i < values.length; i++) {total += values[i];}return total;}', {}))]) failed: db assertion failure

However, defining the map/reduce functions in mongo and running the following command works:

db.things.mapReduce(mm,r,{out:{inline:1}})

The defining difference seems to be the {out:{inline:1}} option. Is there a way to get that into the call in pymongo?

Thanks,

Adam.

---

The problem is related to the 'out' parameter. Starting with MongoDB 1.7.4 the 'out' parameter is required, you must always specify the name of the output collection when invoking map_reduce.

result = db.things.map_reduce(m, r, "output_collection_name")

If you want to perform your whole MapReduce operation in memory, call inline_map_reduce instead.

result = db.things.inline_map_reduce(m, r)

The above examples only work with the latest version of pymongo directly got from the git repository. pymongo 1.9 doesn't work well with MongoDB 1.7.4 or superior.