如何在mongodb中使用mapreduce？

Question

I have the following code in python:

from pymongo import Connection
import bson

c = Connection()
db = c.twitter

ids = db.users_from_united_states.distinct("user.id")

for i in ids:
    count = db.users_from_united_states.find({"user.id":i}).count()
    for u in db.users_from_united_states.find({"user.id":i, "tweets_text": {"$size": count}}).limit(1):
    db.my_usa_fitness_network.insert(u)

I need to get all the users and find the register of each user where the number of tweets_text is equal to the number of times that it appears in the collection (meaning that this document contains ALL the tweets that the same user posted). Then, I need to save it in another collection, or just group it on the same collection.

When I run this code it gives me a number of documents that is less than the ids number

I saw something about mapReduce but I just can't figure out how to use it in my case.

I tried to run another code directly on mongodb but it hasn't worked at all:

var ids = db.users_from_united_states.distinct("user.id")

for (i=0; i< ids.length; i++){
    var count = db.users_from_united_states.find({"user.id":ids[i]}).count()
    db.users_from_united_states.find({"user.id":ids[i], "tweets_text": {$size: count}).limit(1).forEach(function(doc){db.my_usa_fitness_network.insert(doc)})
}

Can you help me please? I have a huge project and I need help. Thank you.

Answer 1

[
    {
        "$group": {
            "_id": "$user.id",
            "my_fitness_data": {
                "$push": "$text"
            }
        }
    },
    {
        "$project": {
            "UserId": "$_id",
            "TweetsCount": {
                "$size": "$my_fitness_data"
            },
            "Tweets": "$my_fitness_data"
        }
    }
    ]