I'm trying to use find() but in function system.js in mongo db but when i run the script the result is
this is my findstored() function
db.system.js.save({
_id:"findstored",
value:function(){
var data = db.counters.find({}, (err, data) => {
data.forEach((data) => {
print("Customer Name: "+data.first_name)
})
return data.first_name;
})
}
})
I just want to display the result with function in system.js. Thank you
Not sure what is the purpose of your function, but this is the right syntax for that function to be saved in system.js:
db.system.js.save({
_id:"findstored",
value:function(){
var ret = "Not found";
db.counters.find().forEach(function(data){
print("Customer Name: "+data.first_name)
ret = data.first_name;
})
return ret;
}
})
And make sure you run db.loadServerScripts(); after saving the function to have it properly loaded.
Do not store application logic in the database. There are performance limitations to running JavaScript inside of MongoDB.
db.system.js.save({
_id:"findUserInformation",
value:function(x){
return db.users.findOne({ "_id" : x }, { firstName:1 }, (err, data) => {
return data
})
}
})
On other shell or command use this findUserInformation function like this
db.loadServerScripts();
findUserInformation("5d7b4ef6f691b71b5097e9cb");
In your question please check return type and run query first and then return data.
In findstored function Application code also is typically most effective when it shares version control with the application itself.
Related
trying to write a Mongo query that will Base64 Decode a field that is Base64 encoded and then perform a simple "like" on the decoded value. I'm following a couple of different posts as well as the Mongo docs, but can't seem to get the syntax correct. I basically want to do a query like this :
db.getCollection('my-collection').find (
{ base64Decode(edmDocumentId): /ni-billing-retro/ }
);
Where base64Decode() is a custom function inserted into system.js.
Posts:
----------------
Export text stored as Bindata in mongodb
How to query MongoDB with "like"?
What I've done so far :
I saved the base64Decode() function to the system.js, and I can see the function....https://docs.mongodb.com/manual/tutorial/store-javascript-function-on-server/.
db.system.js.insertOne( {
_id: "base64Decode",
value : function (s) {
var e={},i,k,v=[],r='',w=String.fromCharCode,u=0;
var n=[[65,91],[97,123],[48,58],[43,44],[47,48]];
for(z in n){for(i=n[z][0];i<n[z][1];i++){v.push(w(i));}}
for(i=0;i<64;i++){e[v[i]]=i;}
function a(c){
if(c<128)r+=w(c);else if(c>=192)u=c;else r+=w(((u&31)<<6)+(c&63));
}
for(i=0;i<s.length;i+=72){
var b=0,c,x,l=0,o=s.substring(i,i+72);
for(x=0;x<o.length;x++){
c=e[o.charAt(x)];b=(b<<6)+c;l+=6;
while(l>=8)a((b>>>(l-=8))%256);
}
}
return r;
}
});
I've tried using $where, to no avail...returns ReferenceError: edmDocumentId is not. Added the db.loadServerScripts(); to fix the base64Decode() Reference error.
db.loadServerScripts();
db.getCollection('rapid-document-meta').find (
{ $where: (base64Decode(edmDocumentId) == /ni-billing/) }
);
I've tried doing a straight find (), Unexpected token : Line 2
db.getCollection('rapid-document-meta').find (
{ base64Decode(edmDocumentId): /ni-billing-retro/ }
);
Tried the following from Calling db.system.js Function in $where : ReferenceError: edDocumentId is not defined, even though edmDocumentId is on every single record.
db.loadServerScripts();
db.getCollection('rapid-document-meta').mapReduce (
base64Decode(edDocumentId),
function() {},
{ "out": { "inline": 1 } }
);
Does someone have an example of a find query that uses a custom function from system.js??? Mongo version 4.0.8.
router.get('/wiki/:topicname', function(req, res, next) {
var topicname = req.params.topicname;
console.log(topicname);
summary.wikitext(topicname, function(err, result) {
if (err) {
return res.send(err);
}
if (!result) {
return res.send('No article found');
}
$ = cheerio.load(result);
var db = req.db;
var collection = db.get('try1');
collection.insert({ "topicname" : topicname, "content": result }, function (err, doc){
if (err) {
// If it failed, return error
res.send("There was a problem adding the information to the database.");
}
else {
// And forward to success page
res.send("Added succesfully");
}
});
});
Using this code, I am trying to add the fetched content from Wikipedia in to the collection try1. The message "Added succesfully" is displayed. But the collection seems to be empty. The data is not inserted in the database
The data must be there, mongodb has { w: 1, j: true } write concern options by default so its only returns without an error if the document is truly inserted if there were any document to insert.
Things you should consider:
-Do NOT use insert function, its depricated use insertOne, insertMany or bulkWrite. ref.: http://mongodb.github.io/node-mongodb-native/2.1/api/Collection.html#insert
-The insert methods callback has two parameters. Error if there was an error, and result. The result object has several properties with could be used for after insert result testing like: result.insertedCount will return the number of inserted documents.
So according to these in your code you only test for error but you can insert zero documents without an error.
Also its not clear to me where do you get your database name from. Is the following correct in your code? Are you sure you are connected to the database you want to use?
var db = req.db;
Also you don't have to enclose your property names with " in your insert method. The insert should look something like this:
col.insertOne({topicname : topicname, content: result}, function(err, r) {
if (err){
console.log(err);
} else {
console.log(r.insertedCount);
}
});
Start your mongod server in a correct path,i.e, same path as that of what you are using to check the contents of collection.
sudo mongod --dbpath <actual-path>
I was trying to get familiar with the WriteResult object in mongo, but I can't access any of its values. The docs say the number of values inserted is stored in WriteResult.nInserted. Trying to access nInserted is crashing my server.
var readings = new Readings({
val1: parseInt(Data[0]),
val2: parseInt(Data[1]),
val3: parseInt(Data[2]),
val4: parseInt(Data[3]),
val5: parseInt(Data[4]),
val6: parseInt(Data[5]),
})
var result = readings.save(function (err, post){
if(err){return next(err)}
res.status(201).json(readings)
})
if(result.nInserted > 0){
console.log('wrote to database')
}
else{
console.log('could not write to database')
}
I know the data is being written to the database. I see it in the mongo shell.
The save method on a model instance doesn't return anything. All results are reported via the callback method, so you'd use something like this:
readings.save(function (err, doc, numberAffected){
if(err){return next(err)}
if (numberAffected > 0) {
console.log('updated an existing doc');
} else {
console.log('added a new doc');
}
res.status(201).json(doc)
})
Mongoose doesn't give you access to the full WriteResult, but as long as err is null you can rest assured the save succeeded and it's only a matter of whether an existing doc was updated or a new one was added. Because you're creating a new doc here, numberAffected will always be 0.
I'm using a MEAN stack and with Mongoose. Is there a way to query MongoDB with multiple ids to only return those specific IDs in one query e.g. /api/products/5001,5002,5003
Is this possible or would I need to query each product individually or add an additional attribute to the products and query by that.
Update: To clarify as suggested below I've managed to get it partially working using {'_id': { $in: [5001,5002,5003]} however I'm having problems figuring out how to pass the list from the api url to the find function.
Using Express.js for router
router.get('/list/:ids', controller.showByIDs);
exports.showByIDs = function(req, res) {
Product.find({'_id': { $in: [req.params.ids]}}, function (err, product) {
if(err) { return handleError(res, err); }
if(!product) { return res.send(404); }
return res.json(product);
})
};
Then trying /api/products/list/5001 works however /api/products/list/5001,5002 doesn't. I'm not sure if it's a syntax problem in the url or my router code that needs to change or the controller.
You can use the $in operator to query for multiple values at once:
Products.find({_id: {$in: [5001, 5002, 5003]}}, function (err, products) { ... });
On the Express side, you need to use a format for the ids parameter that lets you split it into an array of id values, like you had in your first example:
/api/products/5001,5002,5003
Then in your route handler, you can call the split function on the req.params.ids string to turn it into an array of id values that you can use with $in:
exports.showByIDs = function(req, res) {
var ids = req.params.ids.split(',');
Product.find({'_id': { $in: ids}}, function (err, product) {
if(err) { return handleError(res, err); }
if(!product) { return res.send(404); }
return res.json(product);
})
};
Ok, still in my toy app, I want to find out the average mileage on a group of car owners' odometers. This is pretty easy on the client but doesn't scale. Right? But on the server, I don't exactly see how to accomplish it.
Questions:
How do you implement something on the server then use it on the client?
How do you use the $avg aggregation function of mongo to leverage its optimized aggregation function?
Or alternatively to (2) how do you do a map/reduce on the server and make it available to the client?
The suggestion by #HubertOG was to use Meteor.call, which makes sense and I did this:
# Client side
Template.mileage.average_miles = ->
answer = null
Meteor.call "average_mileage", (error, result) ->
console.log "got average mileage result #{result}"
answer = result
console.log "but wait, answer = #{answer}"
answer
# Server side
Meteor.methods average_mileage: ->
console.log "server mileage called"
total = count = 0
r = Mileage.find({}).forEach (mileage) ->
total += mileage.mileage
count += 1
console.log "server about to return #{total / count}"
total / count
That would seem to work fine, but it doesn't because as near as I can tell Meteor.call is an asynchronous call and answer will always be a null return. Handling stuff on the server seems like a common enough use case that I must have just overlooked something. What would that be?
Thanks!
As of Meteor 0.6.5, the collection API doesn't support aggregation queries yet because there's no (straightforward) way to do live updates on them. However, you can still write them yourself, and make them available in a Meteor.publish, although the result will be static. In my opinion, doing it this way is still preferable because you can merge multiple aggregations and use the client-side collection API.
Meteor.publish("someAggregation", function (args) {
var sub = this;
// This works for Meteor 0.6.5
var db = MongoInternals.defaultRemoteCollectionDriver().mongo.db;
// Your arguments to Mongo's aggregation. Make these however you want.
var pipeline = [
{ $match: doSomethingWith(args) },
{ $group: {
_id: whatWeAreGroupingWith(args),
count: { $sum: 1 }
}}
];
db.collection("server_collection_name").aggregate(
pipeline,
// Need to wrap the callback so it gets called in a Fiber.
Meteor.bindEnvironment(
function(err, result) {
// Add each of the results to the subscription.
_.each(result, function(e) {
// Generate a random disposable id for aggregated documents
sub.added("client_collection_name", Random.id(), {
key: e._id.somethingOfInterest,
count: e.count
});
});
sub.ready();
},
function(error) {
Meteor._debug( "Error doing aggregation: " + error);
}
)
);
});
The above is an example grouping/count aggregation. Some things of note:
When you do this, you'll naturally be doing an aggregation on server_collection_name and pushing the results to a different collection called client_collection_name.
This subscription isn't going to be live, and will probably be updated whenever the arguments change, so we use a really simple loop that just pushes all the results out.
The results of the aggregation don't have Mongo ObjectIDs, so we generate some arbitrary ones of our own.
The callback to the aggregation needs to be wrapped in a Fiber. I use Meteor.bindEnvironment here but one can also use a Future for more low-level control.
If you start combining the results of publications like these, you'll need to carefully consider how the randomly generated ids impact the merge box. However, a straightforward implementation of this is just a standard database query, except it is more convenient to use with Meteor APIs client-side.
TL;DR version: Almost anytime you are pushing data out from the server, a publish is preferable to a method.
For more information about different ways to do aggregation, check out this post.
I did this with the 'aggregate' method. (ver 0.7.x)
if(Meteor.isServer){
Future = Npm.require('fibers/future');
Meteor.methods({
'aggregate' : function(param){
var fut = new Future();
MongoInternals.defaultRemoteCollectionDriver().mongo._getCollection(param.collection).aggregate(param.pipe,function(err, result){
fut.return(result);
});
return fut.wait();
}
,'test':function(param){
var _param = {
pipe : [
{ $unwind:'$data' },
{ $match:{
'data.y':"2031",
'data.m':'01',
'data.d':'01'
}},
{ $project : {
'_id':0
,'project_id' : "$project_id"
,'idx' : "$data.idx"
,'y' : '$data.y'
,'m' : '$data.m'
,'d' : '$data.d'
}}
],
collection:"yourCollection"
}
Meteor.call('aggregate',_param);
}
});
}
If you want reactivity, use Meteor.publish instead of Meteor.call. There's an example in the docs where they publish the number of messages in a given room (just above the documentation for this.userId), you should be able to do something similar.
You can use Meteor.methods for that.
// server
Meteor.methods({
average: function() {
...
return something;
},
});
// client
var _avg = { /* Create an object to store value and dependency */
dep: new Deps.Dependency();
};
Template.mileage.rendered = function() {
_avg.init = true;
};
Template.mileage.averageMiles = function() {
_avg.dep.depend(); /* Make the function rerun when _avg.dep is touched */
if(_avg.init) { /* Fetch the value from the server if not yet done */
_avg.init = false;
Meteor.call('average', function(error, result) {
_avg.val = result;
_avg.dep.changed(); /* Rerun the helper */
});
}
return _avg.val;
});