I was going through the mongodb and nodejs course on MongoDBUniversity and one of the task involves finding the documents which has the highest recorded temperature for any state and then add a field "month_high" to it.I am able to find the documents for the state with the highest temperature but am unable to update it. The code is as below.
Can someone tell me what might I be doing wrong?
var MongoClient=require('mongodb').MongoClient;
MongoClient.connect('mongodb://localhost:27017/course',function(err,db){
var cursor=db.collection("weather").find();
cursor.sort({"State":1,"Temperature":-1});
var oldState,newState;
cursor.each(function(err,doc){
if(err)throw err;
if(doc==null){
return db.close();
}
newState=doc.State;
if(newState!=oldState){
var operator={'$set':{"month_high":true}};
var query={"_id":doc._id};
console.log(doc._id+" has temp "+doc.Temperature+" "+doc.State);
db.collection("weather").update(doc,operator,function(err,updated){
console.log("hi");//---->Never Logs
if(err)throw err;
// console.log(JSON.stringify(updated));
})
}
oldState=newState;
});
});
I'm not 100% sure, but given the syntax reported on the docs you might have to specify the options parameter even if not using it:
db.collection("weather").update(doc,operator, options, function(err,updated)
Also, the connection might get closed before the callbacks are called. Does it change anything if you remove the db.close() call?
Collection name is 'data'. In this homework 'weather' is database name.
See
https://education.mongodb.com/courses/10gen/M101JS/2013_October/courseware/CRUD/Homework_2.2/
> use weather
switched to db weather
> db.data.findOne()
Related
I am trying to create a capped collection in MongoDB using NodeJS driver.
db.createCollection(req.body.name,options,function onCreateCollection(mongoErr,mongoCollection){
if(mongoErr){
...
}else{
console.log( mongoCollection.collectionName );
...
}
});
The collection name prints on the console but show collections does not list it. I tried a hyphenated name this-is-a-collection.
Why is that?
Also, what are the limitations in naming a collection?
I don't know why your code doesn't work. But I just tried to create a collection with the hyphenated name this-is-a-collection with this simple script, it worked.
var MongoClient = require('mongodb').MongoClient;
var url = 'mongodb://localhost:27017/db';
MongoClient.connect(url, function(err, db) {
console.log("Connected correctly to server");
db.createCollection('this-is-a-collection', { capped : true, size : 10000 } ,function onCreateCollection(err,mongoCollection){
if(err){
console.log(err);
} else {
console.log(mongoCollection.collectionName);
}
db.close();
});
});
And in the CLI :
MBP:mongo sapher$ mongo
MongoDB shell version: 3.0.5
connecting to: test
....
> use db
switched to db db
> show collections
system.indexes
this-is-a-collection
You can follow this link to get more info on MongoDB naming restrictions.
For naming convention, I personnaly use snake case like remote_users. I think this is the most elegant way to name a collection. Naming isn't that important as long as you stay consistent.
As it turns out, on older version of the driver 1.4.x, creating a capped collection without specifying the size option doesn't result in an error. It even returns a success response. On the newer version, 2.0.x, it does result in an error.
For a capped collection, size is needed while max is optional. The docs are slightly ambiguous as they do not state that you need a size to create a capped collection.
I am writing an API with Node and Express, and use MongoDB as the database.
It has worked for a long time now, but today when I wrote some changes to a model, the server won't start anymore. I originally thought that a recent code change caused it, but even if I stash my changes and reset to a working state, the error occurs.
This is the error:
TypeError: pool.getAll is not a function
at MongoCR.auth (/location/of/project/node_modules/mongodb/node_modules/mongodb-core/lib/auth/mongocr.js:56:26)
at Server.auth (/location/of/project/node_modules/mongodb/node_modules/mongodb-core/lib/topologies/server.js:1019:40)
at ReplSet.auth (/location/of/project/node_modules/mongodb/node_modules/mongodb-core/lib/topologies/replset.js:572:17)
at ReplSet.auth (/location/of/project/node_modules/mongodb/lib/replset.js:438:23)
at authenticate (/location/of/project/node_modules/mongodb/lib/db.js:1319:21)
at Db.authenticate (/location/of/project/node_modules/mongodb/lib/db.js:1356:44)
at /location/of/project/node_modules/mongodb/lib/mongo_client.js:414:25
at /location/of/project/node_modules/mongodb/lib/db.js:221:5
at connectHandler (/location/of/project/node_modules/mongodb/lib/replset.js:335:7)
at g (events.js:260:16)
If I comment out all database connections the app runs. I've tried changing database, but it does not work either. I found this and this question and answer, and double checked versions and that all db-calls have callback-methods. I've used the last argument as the callback for calls that affect one entry, and toArray(function(err, result){}) when there are multiple entries returned.
Mongo version is 2.6.3, and I use the Node-mongodb driver.
I connect with
var mongo = require('mongodb').MongoClient;
var url = process.env.MONGODB || 'mongodb://localhost:27017/test';
var myCollection;
mongo.connect(url, function(err, db) {
if(err) console.log(err);
myCollection = db.collection('myCollection');
});
Then I have methods for e.g. find:
myCollection.find({}).toArray(function(err, result){
// work with result
});
I'm lost - thanks in advance.
This code is intended to make changes in bulk to all the documents in a MongoDB collection. However there is no change at all to the documents in the collection after running this code. What is wrong with it?
var mongoose = require('mongoose'),
async = require('async'),
Person = require('../../model/Person');
mongoose.connect('mongodb://localhost/people-questions');
var db = mongoose.connection;
db.on('error', console.error.bind(console, 'connection error:'));
Person.find(function (err, people) {
if (err) return console.error(err);
//download bio info
async.each(people, function(person, callback) {
person.birthdateYear = '01';
person.save();
callback();
});
mongoose.connection.close();
});
I have verified that there are no changes made by leaving a mongo cli instance open in Terminal and running db.people.find(); to see the field is not updated at all, and also queries such as db.people.find({ "_id" : ObjectId("5379e6e21fe1e8e2fc364d17")});, referencing specific IDs to verify that my Javascript code is indeed connected to the right database and is using the right collection (that ID came from a previous script using identical connection details to print out document IDs).
Also, I am using Mongoose. The Mongoose Schema was updated to include extra fields like birthdateYear after the original documents were created, but from the googling and Mongo Docs reading that I've done already it appears as though Schema changes shouldn't require any special work - you can set attributes against documents with the updated schema right away (should be able to anyway).
The reason the updates are not persisted is that the connection to MongoDB is closed before the save() callbacks have a chance to complete. By ensuring all the save() callbacks complete before closing the connection, the data is saved.
person.save is an async function
try something like
person.save (function(err){
if(err) console.log(err);
callback();
});
I think this is a very simple question? I am a beginner trying to learn mongo with node.
Once I have saved something to a collection, how can I pull it out in simple var format?
db.highschools.save({
hsid :10,
name :"Johnson High School",
location:"San Diego, CA"
});
I simply want to store a var as 'Johnson High School'.
My failed attempts that have returned undefined are as follows...
var hsName = db.highschools.find({hsid:10}).name;
var hsName = db.highschools.find({hsid:10}).name.str;
Pretty sure I'm missing the big picture here, would someone please be kind enough to help me figure this out?
Use findOne instead:
var hsName = db.highschools.findOne({hsid:10}).name;
Also, note that this is a Mongo script, not a NodeJS script.
You'll need to make it async when you write the logic in NodeJS.
db.collection('students', function(err, collection) {
collection.findOne({hsid:10}, function(err, student) {
if (err) { throw err; }
console.log(student.name);
});
});
If you're confident that there should be only one result, then you can use the shortcut method findOne which simply calls find internally with a limit of one. If you were to use find, it returns an array of matches.
In the following code:
var MongoClient = require('mongodb').MongoClient;
MongoClient.connect('mongodb://localhost:27017/db_name', function(err, db){
if (err) throw err;
var collection = db.collection('col_name');
console.log(collection.find().toArray(function(err, items){}));
});
When I run the above, it doesn't return any results and instead returns undefined. What am I missing?
Also, in order to confirm there exist some collections on the db, which there are, I tried to add console.log(db.getCollectionNames());, but it looks like it has no such method in Node.js driver. So is it still possible to confirm the existence of collections? (Anyway I just want to use it as debug in these situations - usually I don't need the method though).
Thanks.
Don't log your entire find() function, do the checking in the callback:
collection.find().toArray(function(err, items){
console.log(items);
});
For the getCollectionNames() part, the method is actually called collectionNames() in the mongodb native driver :
db.collectionNames(function (err, list) {console.log(list)});