Develop Reference

MongoDB unset removes everything in child

I have a db structure like this:
{ "_id" : ObjectId("5fd48e12e5e0fd174c1a7260"),
"races" : {
"example1" : { "date" : "12/18/2020", "status" : "pending" },
"example2" : { "date" : "12/18/2020", "status" : "domestic" }
}
and I am attempting to just remove example 1 by using the following block of code(javascript):
self.db = client.db("authinfo");
self.collection = self.db.collection("users");
this.delete_both_races = function (user1) {
self.collection.updateOne({user:user1} ,{$unset:{races:"example1"}} ,function(error,result){});
same thing happens when running the following command in the mongo.exe command line program:
db.users.updateOne({user:"anything"} , {$unset:{races:"example1"}})
I get the result of(remaining elements after unsetting) :
{ "_id" : ObjectId("5fd48e12e5e0fd174c1a7260") }
desired result :
{ "_id" : ObjectId("5fd48e12e5e0fd174c1a7260"),
"races" : {
"example2" : { "date" : "12/18/2020", "status" : "domestic" }
}

You should unset races.example1 instead of races.
From MongoDB document,
The specified value in the $unset expression (i.e. "") does not impact the operation.
To specify a in an embedded document or in an array, use dot notation.
Mongo Playground

mongodb express.js find object in array

I have this database "equipos" that looks like this:
[
"_id" : ObjectId("5ae4ea9f434d9b51dad68813"),
"team_name" : "Alavés",
"nombre_equipo_movil" : "ALA",
"cantidad_integrantes" : 20,
"partidos_jugados" : 29,
"partidos_ganados" : 10,
"partidos_empatados" : 1,
"partidos_perdidos" : 18,
"goles_a_favor" : 26,
"goles_en_contra" : 45,
"players" : [
{
"dorsal" : 1,
"nombre_jugador" : "Fernando Pacheco",
"edad" : 25,
"nacionalidad" : "España",
"posicion" : "Portero",
"goles" : 0,
"asistencias" : 0,
"amarillas" : 4,
"rojas" : 1
}
...
]
...
]
So I want to check if there is a player with "dorsal" 1 in the team Alavés, and I'm doing this
db.equipos.findOne({"team_name": "Alavés" }, {"players": {$elemMatch: {"dorsal": 1l}}})
the problem is that the response to that query when there is no player with dorsal 1 is:
{ "_id" : ObjectId("5ae4ea9f434d9b51dad68813") }
that being the id of the team. The problem is that when I'm sending that query with express like:
dbo.collection("equipos").findOne(
{"team_name": sReq.body.nombre_equipo }, {"players": {$elemMatch: {"dorsal": sReq.body.dorsal}}},
function(err, res){
I cannot compare res to null to see if it couldn't find the player with that dorsal because I always get the ID of the team...
So how can I check that that player does not exist using that response?

Try with .....dorsal:parseInt(sReq.body.dorsal).... –
Because typeof req.body.xxx==="string";but dorsal type:Number.So you must change string to number with parseInt method.

Don't compare res with null, you can compare Object.keys(res).length == 1 for this situation. I really don't know why your query make that result. But I think this will help you.
if(Object.keys(res).length == 1) {
console.log("No player found!");
} else {
console.log("Hey there!");
}

Mongoose findOne method receives an optional second argument with the fields you want to select.
You should query like this:
dbo.collection("equipos").findOne(
{"team_name": sReq.body.nombre_equipo,
"players": {$elemMatch: {"dorsal": sReq.body.dorsal}}
}, function(err, res){
Notice both fields you want to query you pass as the first argument, and the second argument will be the callback, because you don't tell mongoose which fields to select in this case.

How I can get ID of a new record in mongoDB?

There is such a document structure in MongoDB
{
"_id" : ObjectId("58f7d556aa52ce456672a67e"),
"created" : ISODate("2017-04-19T21:23:34.315Z"),
"context_task" : [
{
"task" : "some text ",
"status" : false,
"_id" : ObjectId("58f7d559aa52ce456672a67f")
}
],
"head" : {
"userID" : "58f48037fc894e19a3f7b81b",
"head_task" : "test record "
},
"__v" : 0
}
I add data to the context_task.task using the following query:
task.findOneAndUpdate({"_id": req.body.id_project},
{$push: {'context_task': {'task': req.body.input_task,'status': false}}},{new: true},
function (err, doc) {
if (err) return next(err);
var body = req.body.id_project+","+req.body.input_task;
console.log(doc);
res.status(200).send(body);
});
Tell me, how can I get the context_task._id of a new record after inserting it? In this case, the entire document is returned.

Every mongo document is associated with a default _id, in case not provided it will be ObjectId.
In case you want to use _id value for any other purpose, why don't you have your own _id value, which has to be unique throughout collection. The value can be of any datatype as well as nested also.

Can't get data from MongoDB database for web app

I'm new to using MongoDB. Currently, I am making a web application that requires some data storage. I established an HTTP server on Node.js that runs on localhost:3000. I also built a virtual development environment using Vagrant and VirtualBox. I am accessing the Mongo shell from PuTTy (if that is relevant at all). Before incorporating MongoDB, it worked fine as I was storing the data in the Node.js program memory.
This web app is an online to-do-list. The first error that I am getting is with the get route. The list of "to-do"s that I have inserted into the Mongo database would not appear on the site in localhost. It seems to not be getting the data from the database. The second error that I am getting is with the post route. When I insert a "to-do" through the user interface at localhost and I refresh the page, the to-do-list on localhost gets updated with that particular to-do (but not with the ones I inserted in the database). But, it doesn't seem to add it into the database, and I still get this error on the console:
vagrant#precise32:~/app$ node server.js
{ description: 'descTest3', tags: [ 'tagTest3' ] }
Mongoose: mpromise (mongoose's default promise library) is deprecated, plug in your own promise library instead: http://mongoosejs.com/docs/promises.html
I'm not sure why I got that error since I do not seem to be using any promises.
server.js
var express = require("express"), http = require("http"), app = express(), mongoose = require("mongoose");
app.use(express.static(__dirname + "/client"));
app.use(express.urlencoded());
mongoose.connect('mongodb://localhost/WatNext');//connect to the WatNext data store in mongoDB
var ToDoSchema = mongoose.Schema({
"description": String,
"tags": [ String ] //array of Strings
});
var ToDo = mongoose.model("ToDo", ToDoSchema)
http.createServer(app).listen(3000);
//get and post routes:
app.get("/toDos.json", function (req, res) {
ToDo.find({}, function (err, toDos) {
if (err != null){
console.log(err);
}
res.json(toDos);
});
});
app.post("/todos", function (req, res) {
console.log(req.body);
var addedToDo = new ToDo({"description" : req.body.description, "tags" : req.body.tags});
//save function saves object into the database
addedToDo.save(function (err, result) {
if (err != null){//if there is an error
console.log(err);
res.send("ERROR SAVING");
}
else {
ToDo.find({}, function (err, result) {
if (err != null){//if there is an error in finding
res.send("ERROR FINDING");
}
res.json(result);
});
}
});
});
app.js
var main = function (toDoObjects) {
//do stuff with ToDoObjects including outputting the list of ToDos
};
$(document).ready(function() {
$.getJSON("toDos.json", function(toDoObjects) {
main(toDoObjects);
})
});
mongo shell
> show dbs
WatNext 0.0625GB
local 0.03125GB
> use WatNext
switched to db WatNext
> show collections;
system.indexes
toDoCollection
todos
> db.toDoCollection.find();
{ "_id" : ObjectId("58b38dd8fb355f57162d9cf1"), "description" : "Get groceries and eat afterwards", "tags" : [ "shopping", "chores" ] }
{ "_id" : ObjectId("58b38dd8fb355f57162d9cf2"), "description" : "Make up some new To-Dos", "tags" : [ "writing", "work" ] }
{ "_id" : ObjectId("58b38dd8fb355f57162d9cf3"), "description" : "Prep for Monday's class", "tags" : [ "work", "teaching" ] }
{ "_id" : ObjectId("58b38dd8fb355f57162d9cf4"), "description" : "Answer emails", "tags" : [ "work" ] }
{ "_id" : ObjectId("58b38dd8fb355f57162d9cf5"), "description" : "Take April to the park", "tags" : [ "chores", "pets" ] }
{ "_id" : ObjectId("58b38dd8fb355f57162d9cf6"), "description" : "Finish writing this book", "tags" : [ "writing", "work" ] }
EDIT:
I found out it was just an error of naming.
I also found out that
mongoose.Promise = require("bluebird");
solved the problem with the promise error. Remember to install the module first though:
npm install --save bluebird

I found out what was wrong. It was an error in naming for the GET and POST routes. It should have been:
app.get("/todos.json", function (req, res) { //get the data from the collection called 'todos' in MongoDB
as well as:
$.getJSON("todos.json", function(toDoObjects) {
I should have used the todos collection instead of toDoCollection:
"description" : "descTest1", "_id" : ObjectId("58b39a1fb1a30305075408fa"), "tags" : [ "tagTest2" ], "__v" : 0 }
{ "description" : "descTest2", "_id" : ObjectId("58b4c837d47a5604c7c0609a"), "tags" : [ "tagsTest2" ], "__v" : 0 }
{ "description" : "descTest3", "_id" : ObjectId("58b4ca0491f4c804d200cda9"), "tags" : [ "tagTest3" ], "__v" : 0 }
{ "description" : "descTest4", "_id" : ObjectId("58b4e636b71d0a05ebb7a71a"), "tags" : [ "tagTest4" ], "__v" : 0 }
{ "description" : "descTest5", "_id" : ObjectId("58b60211428520053a4714ed"), "tags" : [ "tagTest5" ], "__v" : 0 }
{ "_id" : ObjectId("58b6037839e65d96e13cf68e"), "description" : "descTestMONGO", "tags" : [ "tagTestMONGO" ] }
{ "_id" : ObjectId("58b605b339e65d96e13cf690"), "description" : "Take April to the park", "tags" : [ "chores", "pets" ] }

Mongoose - Loop an array of embedded docs to .push new value to a field en masse?

I have a doc with an array of embedded docs ("comments"), and an example that looks like this:
{
"_id" : ObjectId("539e9213209e743d107e7202"),
"article" : "article1",
"comments" : [
{
"comment" : "comment1",
"created" : ISODate("2014-06-16T06:43:38Z"),
"_id" : ObjectId("539e921a209e743d107e7203"),
"read" : {
"marked" : false
},
"timesent" : {
"datetime" : "Mon Jun 16 2014 02:43:38 GMT-0400 (EDT)",
"hour" : 2,
"minute" : "43",
"second" : 38,
"am" : true,
"month" : 5,
"day" : 16,
"year" : 2014
}
}
]
}
For each comment in the comments array, is there a way to batch update the field "read" : {"marked" : true}?
Am working with node.js, and have something like this in mind (the questionable portion begins with
if (req.body.readComment) {..
// update the article with this id (accessed by PUT at
// http://localhost:4200/api/v1/articles/:article_id)
.put(function(req, res) {
Article.findById(req.params.article_id, function(err, article) {
if (err)
res.send(err);
if (req.body.comment) {
article.comments.push({
comment : req.body.comment,
timesent :
{
datetime : req.body.datetimeNow,
hour : req.body.hourNow,
minute : req.body.minuteNow,
second : req.body.secondNow,
am : req.body.amNow,
month : req.body.monthNow,
day : req.body.dayNow,
year : req.body.yearNow
},
read :
{
marked : req.body.readComment,
datetime : req.body.readCommentDatetime
},
created : req.body.datetimeNow
});
} // if newComment
if (req.body.readComment) {
var comments = // some sort of .find ?
var embeddedDoc;
for (var i=0, length=comments.length; i < length; i++){
embeddedDoc = comments[i];
embeddedDoc_id = // something to find the embedded doc_id ?
console.log(i);
article.comments.push({ // maybe push to the embedded doc_id
read :
{
marked : req.body.readComment,
datetime : req.body.readCommentDatetime
}
});
};
} // if readComment == true (from ajax .put)
// save the article, and check for errors
article.save(function(err) {
if (err)
res.send(err);
res.json({ message: 'Update "' + req.params.article_id });
});
});
})

Well as each comment would need to be identified within the array, the term "Bulk" doesn't really apply as they would be inherently separate. As for being able to just say "Update all of these 'comments' and mark them as true", that is not directly supported.
But on the other hand you can streamline this with Bulk update operations. So for a "list" of "comment" _id values you could do this:
var bulk = collection.initializeOrderedBulkOp();
comments.forEach(function(commentId) {
bulk.find({ "comments._id": commentId }).updateOne({
"$set": { "comments.$.read.marked": false }
});
counter++;
if ( counter % 500 == 0 ) {
bulk.execute(function(err,result) {
// do something with the result
bulk = collection.initializeOrderedBulkOp();
counter = 0;
});
}
});
// Catch any under or over the 500's
if ( counter > 0 )
bulk.execute(function(err,result) {
// do something with the result here
});
That at least avoids you sending an update "over the wire" to the server instance for every single "comment" _id you send into the API. By batching the results this results in less traffic and less time waiting for the response in the callback.
You can likely better this example with "async" so even looping the input list is a non-blocking operation. The batch sizes can vary, but this is just a safe example to stay under the 16MB BSON hard limit, as the whole "request" is equal to one BSON document.