In my Node.js (Express) app that uses Monk, I need to render a list of all collections in the MongoDB database.
Is there a way to get the list of collections in the database using Monk?
This wil basicaly do that, but it takes some digging into the underlying driver to do so:
var db = require('monk')('localhost/test');
db.on("open",function() {
console.log(
db.driver._native.command(
{ "listCollections": 1 },
function(err,result) {
console.log( result.cursor.firstBatch.map(function(el) {
return el.name;
}))
}
)
);
});
The driver command is of course "listCollections" and those are the basic hoops you need to jump through to get there
Related
I was doing a server using nodejs, it need get data from mongodb. I retrieve data after require(../db.js). Somebody said the mongodb needn't be close in nodejs,because nodejs is a single process.....
My question: Need I call dropCollection to close the collection after invoked the db function many times;and How to do?Where to do that? Please,Thanks.
You dont need to drop the collection after invoking db functions,simply call db.close() though it is not needed. But if you want to do it , you can do it as follows:
var dropRestaurants = function(db, callback) {
db.collection('restaurants').drop( function(err, response) {
console.log(response)
callback();
});
};
I have a mongodb Relationships collection that stores the user_id and the followee_id(person the user is following). If I query for against the user_id I can find all the the individuals the user is following. Next I need to query the Users collection against all of the returned followee ids to get their personal information. This is where I confused. How would I accomplish this?
NOTE: I know I can embed the followees in the individual user's document and use and $in operator but I do not want to go this route. I want to maintain the most flexibility I can.
You can use an $in query without denormalizing the followees on the user. You just need to do a little bit of data manipulation:
Relationship.find({user_id: user_id}, function(error, relationships) {
var followee_ids = relationships.map(function(relationship) {
return relationship.followee_id;
});
User.find({_id: { $in: followee_ids}}, function(error, users) {
// voila
});
};
if i got your problem right(i think so).
you need to query each of the "individuals the user is following".
that means to query the database multiple queries about each one and get the data.
because the queries in node.js (i assume you using mongoose) are asynchronies you need to get your code more asynchronies for this task.
if you not familier with the async module in node.js it's about time to know it.
see npm async for docs.
i made you a sample code for your query and how it needs to be.
/*array of followee_id from the last query*/
function query(followee_id_arr, callback) {
var async = require('async')
var allResults = [];
async.eachSerias(followee_id_arr, function (f_id, callback){
db.userCollection.findOne({_id : f_id},{_id : 1, personalData : 1},function(err, data){
if(err) {/*handel error*/}
else {
allResults.push(data);
callback()
}
}, function(){
callback(null, allResults);
})
})
}
you can even make all the queries in parallel (for better preformance) by using async.map
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 follow a tutorial with Meteor I try to create a collection, both for client and server. Here is my code:
var lists = new Meteor.Collection("Lists");
if (Meteor.isClient) {
}
if (Meteor.isServer) {
Meteor.startup(function () {
// code to run on server at startup
});
}
As tutorial I have read, when run on server, if I open chrome console and type lists I will receive Meteor.Collection. But when I tried on my machine, I received error:
Reference error. lists is not define
Have I done something wrong? Please tell me.
Thanks :)
Also you can put all your collections inside the /lib/collection.js route (for better practices).
So with that we ensure that meteor loads first the collections, and they will be available on both client/server.
you should remove Autopublish/insecure package, to avoid meteor sends all the collections when load and to control who can or not insert/remove/update on the collections.
meteor remove autopublish
meteor remove insecure.
So a simple collection will look like this.
//lib/collection.js
Example = new Mongo.Collection("Example") //we create collection global
if(Meteor.isClient) {
Meteor.subscribe('Example') //we subscribe both after meteor loads client and server folders
}
now on /server/collections.js
Meteor.publish('Example', function(){
return Example.find(); //here you can control whatever you want to send to the client, you can change the return to just return Example.find({}, {fields: {stuff: 1}});
});
// Here we control the security of the collections.
Example.allow({
insert: function(userId, doc) {
if(Meteor.userId()){
return true; //if the user is connected he can insert
} else{
return false// not connected no insert
}
},
update: function(userId, doc, fields, modifier) { //other validation },
remove: function(userId, doc) { //other validation },
});
Just to try to explain a little more deep the Collection here on meteor, hope it help you GL
I think you have autopulish/autosubscribe turned off. Try
if (Meteor.isClient) {
Meteor.subscribe('lists');
}
if (Meteor.isServer){
Meteor.publish('lists',function(){
return Lists.find();
});
}
For your naming, I'd also recommend you reverse the way you're capitalizing your collections. So instead it would be
var Lists = new Meteor.Collection("lists");
And finally, look at https://github.com/matteodem/meteor-boilerplate for your directory structure so you don't have to do the if meteor.is stuff anymore.
Edit
Full code should look like:
var Lists = new Meteor.Collection("lists");
if (Meteor.isClient) {
Meteor.subscribe('lists');
}
if (Meteor.isServer){
Meteor.publish('lists',function(){
return Lists.find();
});
}
All of your script source files are wrapped in a function closure as part of the build process. In order for your collection to be visible outside of that file (or in your case - attached to the window object) you will need to declare it as a global variable:
Lists = new Meteor.Collection('lists');
Note the lack of var. As #thatgibbyguy pointed out, the accepted pattern is to capitalize collection variables, and camelcase collection names.
Hi im developing an app with nodeJS, express and a mongoDB, i need to take users data from a csv file and upload it to my database this db has a schema designed with mongoose.
but i don know how to do this, what is the best approach to read the csv file check for duplicates against the db and if the user (one column in the csv) is not here insert it?
are there some module to do this? or i need to build it from scratch? im pretty new to nodeJS
i need a few advices here
Thanks
this app have an angular frontend so the user can upload the file, maybe i should read the csv in the front end and transform it into an array for node, then insert it?
Use one of the several node.js csv libraries like this one, and then you can probably just run an upsert on the user name.
An upsert is an update query with the upsert flag set to true: {upsert: true}. This will insert a new record only if the search returns zero results. So you query may look something like this:
db.collection.update({username: userName}, newDocumentObj, {upsert: true})
Where userName is the current username you're working with and newDocumentObj is the json document that may need to be inserted.
However, if the query does return a result, it performs an update on those records.
EDIT:
I've decided that an upsert is not appropriate for this but I'm going to leave the description.
You're probably going to need to do two queries here, a find and a conditional insert. For this find query I'd use the toArray() function (instead of a stream) since you are expecting 0 or 1 results. Check if you got a result on the username and if not insert the data.
Read about node's mongodb library here.
EDIT in response to your comment:
It looks like you're reading data from a local csv file, so you should be able to structure you program like:
function connect(callback) {
connStr = 'mongodb://' + host + ':' + port + '/' + schema; //command line args, may or may not be needed, hard code if not I guess
MongoClient.connect(connStr, function(err, db) {
if(err) {
callback(err, null);
} else {
colObj = db.collection(collection); //command line arg, hard code if not needed
callback(null, colObj);
}
});
}
connect(function(err, colObj) {
if(err) {
console.log('Error:', err.stack);
process.exit(0);
} else {
console.log('Connected');
doWork(colObj, function(err) {
if(err) {
console.log(err.stack);
process.exit(0);
}
});
}
});
function doWork(colObj, callback) {
csv().from('/path/to/file.csv').on('data', function(data) {
//mongo query(colObj.find) for data.username or however the data is structured
//inside callback for colObj.find, check for results, if no results insert data with colObj.insert, callback for doWork inside callback for insert or else of find query check
});
}