Suppose I have a mongodb query as such :
db.collection('users').updateOne({name:name},{$set:{data:data}})
I want to use this query across many functions and I want to reuse it and avoid writing the same query over and over again.
You can re-use query only if you provide condition and object data in function. Check below code it may help you to get the same result.
This will be your model function.
user.updateUser = function (conditon, updateData, callback) {
userModel.update(conditon, updateData).exec(callback);
}
You can call this function like as below.
userModel.updateUser({_id: userId, name:name},{$set:{data:data}}, (err, result) => {
console.log(err, result);
});
Related
I am using the async eachSeries function with mongoose that allows me to iterate through the array and save to the database with "boardDetails" and "newBoardDetails". The "saver" parameter will contain one of the two array items each time the object is saved to the database. My question is, for "newBoardDetails" I would not like to use the .save() function but I would like to use the .findByIdAndUpdate() function meaning that I would need to do something different on my second run through. How could I accomplish this?
var mongooseSave = [ boardDetails, newBoardDetails];
async.eachSeries(mongooseSave, function(saver, asyncdone) {
saver.save(asyncdone);
}, function(err) {
if (err) return console.log(err);
});
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'm trying to use async eachSeries in order to code what's the report count for every category. Categories and Reports and stored in separate collections, then I first get available categories and perform a count search on them.
This is my code:
Category.find({},{_id:0, name: 1}, function (err, foundCategories) {
async.eachSeries(foundCategories,
function (item,callback) {
Report.count({category: item.name}, function (err,count) {
var name = item.name;
console.log(count);
return callback(null,{name: count});
});
}
,function (err, results) {
if (err)
response.send(err);
response.send(JSON.stringify(results));
});
});
The problem is that I'm receiving nothing, the console.log outputs actual numbers there, what am I doing wrong?
The API of eachSeries does not provide any results to the final callback - only an error in the failure case. In the success case, it's just a pure control flow "eachSeries is done" indicator, but does not provide a mechanism for passing values from the worker function. mapSeries does provide the functionality you need.
Similar as Peter's answer, async.waterfall provides you with waterfall-execution of your functions, while passing a return value to the next async function in the waterfall chain.
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
});
}
I got a MySQL query where I ask for the values in a specific field with the help of the SELECT statement. My question is: How do I get the value of the query ? When I render the template with my current code I receive following output on my page [object Object]. I have the following Code:
var network;
function query(sql, callback) {
connection.query(sql, function(err, rows) {
if (err) {
callback(err, null);
} else {
callback(rows);
res.render('index.hjs', { Mysql : network });
console.log(network);
}
});
}
query("SELECT testString FROM test", function(results){
network = results;
});
There are a couple of corrections in your code. Nothing wrong but just good practice. In error callback, you are sending two arguments but in actual query callback function, you are using only one argument.
Second thing is that res will be undefined inside query function. (Of course, unless you have it inside request handler, which spoils the purpose of having it as a function)
Without your database structure and code structure, this is the best I can do to help you.