Loop through Mongo Collection and update a field in every document - node.js

Question

I have Dates in one Collection that were inserted incorrectly, and are in a simple "2015-09-10" string format.
I'd like to update them to correct ISO Date format.
I've tried looping through Mongo with forEach() but I don't know the shell well enough on how to update each document in the collection.
So far I'm at this point:
db.getCollection('schedules').find({}).forEach(function (doc) {
doc.time = new Date( doc.time ).toUTCString();
printjson( doc.time );
// ^ This just prints "Invalid Date"
// Also none of the below work when I try saving them
//doc.save();
//db.getCollection('schedules').save(doc);
});
What's missing here?

Answer 1

The best way to do this is using "Bulk" operations
var collection = db.getCollection('schedules');
var bulkOp = collection.initializeOrderedBulkOp();
var count = 0;
collection.find().forEach(function(doc) {
bulkOp.find({ '_id': doc._id }).updateOne({
'$set': { 'time': new Date(doc.time) }
});
count++;
if(count % 100 === 0) {
// Execute per 100 operations and re-init
bulkOp.execute();
bulkOp = collection.initializeOrderedBulkOp();
}
});
// Clean up queues
if(count > 0) {
bulkOp.execute();
}

Answer 2

Just write a for loop using .find(), and update each result. For instance, in Python/PyMongo, let's assume we have a collection called 'movies' that we want to update by adding a field called 'reviews', whose value we want to be an array of five objects with 'name' and 'rating' fields. we'll use Faker and random to create some random info for these fields:
from pymongo import MongoClient
from faker import Faker
faker = Faker()
import random
client = MongoClient()
db = client.test
for res in db.movies.find():
db.movies.updata_one(res, {'$set':{'reviews':[{'name':faker.name(), 'rating': random.randint(1,5)} for _ in range(5)]}})
Note that if you're using native Mongo, then you should be using updateOne instead of update_one. I presume a similar approach works in JavaScript, just using for (let res of db.movies.find()) syntax