db = client().demo
db.animals.insert({"x": 1, "tags": ["dog", "cat"]})
db.animals.insert({"x": 2, "tags": ["cat"]})
db.animals.insert({"x": 3, "tags": ["mouse", "cat", "dog"]})
db.animals.insert({"x": 4, "tags": []})
db.animals.aggregate([{
"$unwind": "$tags"
}, {
"$group": {
"_id": "$tags",
"count": {
"$sum": 1
}
}
}, {
"$sort": son([("count", -1), ("_id", -1)])
}])
'''
result:
{u'ok': 1.0,
u'result':
[
{u'_id': u'cat', u'count': 3},
{u'_id': u'dog', u'count': 2},
{u'_id': u'mouse', u'count': 1}
]
}
'''
return total;
}
""")
db = client().demo
result = db.animals.map_reduce(mapper, reducer, "myresults")
for doc in result.find():
print doc
# get more detailed results when desired, by passing full_response=True to map_reduce()
result = db.animals.map_reduce(mapper, reducer, "myresults", full_response=True)
# all of the optional map/reduce parameters are also supported, simply pass them as keyword arguments
result = db.animals.map_reduce(mapper, reducer, "myresults", query={"x": {"$gt": 2}})
# can use SON or collections.OrderedDict to specify a different database to store the result collection
result = db.animals.map_reduce(mapper, reducer, out=son([("replace", "results"), ("db", "outdb")]), full_response=True)
# group() method provides some of the same functionality as SQL’s GROUP BY.
# Simpler than a map reduce you need to provide a key to group by, an initial value for the aggregation and a reduce function.
# group() doesn't work with sharded mongodb configurations.
reducer = code("""
function(obj, prev) {
prev.count++;
}
""")
result = db.animals.group(key={"x": 1}, condition={}, initial={"count": 0}, reduce=reducer)
# because of python dictionaries don't maintain order,
# you should use son or collections.OrderedDict
# where explicit ordering is required e.g. "$sort"
from bson.son import SON as son
from pymongo import MongoClient as client
db = client().demo
db.animals.insert({"x": 1, "tags": ["dog", "cat"]})
db.animals.insert({"x": 2, "tags": ["cat"]})
db.animals.insert({"x": 3, "tags": ["mouse", "cat", "dog"]})
db.animals.insert({"x": 4, "tags": []})
db.animals.aggregate([{"$unwind": "$tags"},
{"$group": {"_id": "$tags", "count": {"$sum": 1}}},
{"$sort": son([("count", -1), ("_id", -1)])}])
'''
result:
{u'ok': 1.0,
u'result':
[
{u'_id': u'cat', u'count': 3},
{u'_id': u'dog', u'count': 2},
{u'_id': u'mouse', u'count': 1}
]
}
'''
