Develop Reference

Map the nested data from other table using promise and async-await

I need the expert advice for this code. I need to know Is there any better way to solve this.
I am using the mongoose for db. I have a dataset like this:
Below is matchTable:
{
_id: 617bc0113176d717f4ddd6ce,
car: [],
status: true
},
{
_id: 617bc0113176d717f4ddd6cg,
car: [
{
aid: '5c1b4ffd18e2d84b7d6febcg',
}
],
status: true
}
And I have a Car table in which car name is there on behalf of id
like this
{ _id: ObjectId('5c1b4ffd18e2d84b7d6febce'), name: 'ford' },
{ _id: ObjectId('5c1b4ffd18e2d84b7d6febcg'), name: 'mitsubishi' },
So I want to make join the data from car table, so that response get name on behalf of aid.
Desired result will be like
{
_id: 617bc0113176d717f4ddd6ce,
car: [],
status: true
},
{
_id: 617bc0113176d717f4ddd6cg,
car: [
{
aid: '5c1b4ffd18e2d84b7d6febcg',
name: 'mitsubishi'
}
],
status: true
}
For that I have to merge the car table on matchTable. I have done this but I want to give some suggestion that is there any better way to do or is it fine. I need expert advice.
const getData = await matchTable.find(
{ status: true }
).lean().exec();
let dataHolder = [];
await Promise.all (
getData.map(async x => {
await Promise.all(
x.car.map(async y => {
let data = await Car.findOne(
{ _id: ObjectId(y.aid) },
{ name: 1 }
).lean().exec();
y.name = '';
if (data) {
y.name = data.name;
}
})
)
// If I return { ...x }, then on response it will return {}, {} on car column
dataHolder.push(x) //So I have chosen this approach
})
);
Please guide me if any better and efficient solution is there. Thanks in advance

You can make use of aggregation here.
const pipeline = [
{
$match : { status : true }
},
{
$unwind: '$matchtable',
},
{
$lookup: {
from: "cars",
localField: "car.aid",
foreignField: "_id",
as: "matchcars"
}
},
{
$addFields: {
"car.carName": { $arrayElemAt: ["$matchcars.name", 0] }
}
},
{
$group: {
_id: "$_id",
cars: { $push: "$matchcars" }
}
}
]
const result = await matchTable.aggregate(pipeline).exec();
Please make sure, aid field inside car array (in matchTable collection) is an ObjectId because its being matched to _id (which is an ObjectId) inside cars collection.

Get some elements from an array mongoDB

In MongoDB shell version v4.4.6
the following code works perfectly.
db['pri-msgs'].findOne({tag:'aaa&%qqq'},{msgs:{$slice:-2}})
But in nodeJs mongoDB the following code doesn't work.
db.collection('pri-msgs').findOne({
tag: 'aaa&%qqq'
}, {
msgs: {
slice: -2
}
})
My document-->
{"_id":{"$oid":"60c4730fadf6891850db90f9"},"tag":"aaa&%qqq","msgs":[{"msg":"abc","sender":0,"mID":"ctYAR5FDa","time":1},{"msg":"bcd","sender":0,"mID":"gCjgPf85z","time":2},{"msg":"def","sender":0,"mID":"lAhc4yLr6","time":3},{"msg":"efg","sender":0,"mID":"XcBLC2rGf","time":4,"edited":true},{"msg":"fgh","sender":0,"mID":"9RWVcEOlD","time":5},{"msg":"hij","sender":0,"mID":"TJXVTuWrR","time":6},{"msg":"jkl","sender":0,"mID":"HxUuzwrYN","time":7},{"msg":"klm","sender":0,"mID":"jXEOhARC2","time":8},{"msg":"mno","sender":0,"mID":"B8sVt4kCy","time":9}]}
Actually what I'm trying to do is Get last 2 itmes from msgs Array where time is greater than 'n'. Here 'n' is a number.

You can use aggregation-pipeline to get the results you are looking for. The steps are the following.
Match the documents you want by tag.
Unwind the msgs array.
Sort descending by msgs.time.
Limit first 2 elements.
Match the time you are looking for using a range query.
Group the documents back by _id.
Your query should look something like this:
db['pri-msgs'].aggregate([
{ $match: { tag: 'aaa&%qqq' } },
{ $unwind: '$msgs' },
{
$sort: {
'msgs.time': -1 //DESC
}
},
{ $limit: 2 },
{
$match: {
'msgs.time': {
$gt: 2 //n
}
}
},
{
$group: {
_id: '$_id',
tag: { $first: '$tag' },
msgs: {
$push: { msg: '$msgs.msg', sender: '$msgs.sender', mID: '$msgs.mID', time: '$msgs.time' }
}
}
}
]);

Update value inside mongodb array object

I'm trying to update a value inside my array of objects.
Looking at the above mongoDB schema what I want is:
Find an expense with the ID match with the _id and need to update the fields with new ones from the req.body.
Just need to update the: expensesType, description, price and status.
The following code is what I tried to do.
First I need to match the right expense and it works fine but when I try to house.save() show me a message 'house.save is not a function'. So I think maybe I need to use a mongoDB function to get the result.
router.put("/editExpense/:id", ensureAuthenticated, (req, res) => {
var id = mongoose.Types.ObjectId(req.params.id);
House.find(
{ "expensesHouse._id": id },
{
members: 1,
name: 1,
description: 1,
address: 1,
type: 1,
user: 1,
userID: 1,
userType: 1,
expensesHouse: { $elemMatch: { _id: id } },
date: 1
}
).then(house => {
console.log(house);
expenseType = req.body.expenseType;
description = req.body.description;
price = req.body.price;
status = req.body.status;
house.save().then(() => {
req.flash("success_msg", "Expenses Updated");
res.redirect("/houses/dashboard");
});
});
});
****** UPDATED ******
After a search I found this updateOne and after adjusts, this is my final result but this way I delete every record..
router.put("/editExpense/:id", ensureAuthenticated, (req, res) => {
var id = mongoose.Types.ObjectId(req.params.id);
House.updateOne(
{ "expensesHouse._id": id },
{
members: 1,
name: 1,
description: 1,
address: 1,
type: 1,
user: 1,
userID: 1,
userType: 1,
expensesHouse: { $elemMatch: { _id: id } },
date: 1
},
{ $set: { "expensesHouse.expenseType": req.body.expenseType } }
).then(house => {
req.flash("success_msg", "Expenses Updated");
res.redirect("/houses/dashboard");
});
});
*********** RESOLUTION ***********
I just fixed the problem the way I show below.
House.updateOne(
{ "expensesHouse._id": id },
{
$set: {
expensesHouse: {
expenseType: req.body.expenseType,
description: req.body.description,
price: req.body.price,
status: req.body.status
}
}
}

You are really close to the answer the problem right now that you are having is syntax difference between find and UpdateOne
This is what Find expects, Check MongoDB docs
db.collection.find(query, projection)
This is what updateOne expects, Check Mongo docs
db.collection.updateOne(
<filter>,
<update>,
{
upsert: <boolean>,
writeConcern: <document>,
collation: <document>,
arrayFilters: [ <filterdocument1>, ... ],
hint: <document|string> // Available starting in MongoDB 4.2.1
}
)
See the Difference? Second parameter should be update not projection because Update one
returns
matchedCount containing the number of matched documents
modifiedCount containing the number of modified documents
upsertedId containing the _id for the upserted document.
A boolean acknowledged as true if the operation ran with write concern or false if write concern was disabled.
So Your code should be
House.updateOne(
{ "expensesHouse._id": id },
{ $set: { "expensesHouse.expenseType": req.body.expenseType } }
).then(house => {
req.flash("success_msg", "Expenses Updated");
res.redirect("/houses/dashboard");
});
});

House.findOneAndUpdate({userId : req.params.userId},
{ $set: { "expensesHouse.$[element].status": req.body.status } },
{ multi:true, arrayFilters: [{ "element.userID" : req.params.subUserId }], new:true })
Your Api reuquest consist of both the IDs (outer as well as inner) like /api/update/:userId/:subUserId

How to insert array items in mongoose?

i'm making a web site with MEAN Stack
I made a schema.
below is the schema.
const StoreSchema = mongoose.Schema({
storename: {
type: String
},
storenumber: {
type: Number
},
product: [{
pname: String,
pcode: Number,
price: String,
detail: String
}]
});
product is array.
when i make this schema, mongoose make it like this.
_id:5c3afaa96649e84364aab24b
storenumber:1
product:Array
__v:0
now there is a problem .
i want to insert values to pname, pcode, price, detail in product array.
but i can't push the values to the array.
below is the inserting value code.
module.exports.addProd = function(newProd, callback) {
Store.updateOne({
storenumber: number
}, {
$push: {
pname: newProd.pname
},
$push: {
pcode: newProd.pcode
},
$push: {
price: newProd.price
},
$push: {
detail: newProd.detail
}
}, callback);
}
but it doesn't work.
even i wrote product.
the values in newProd are all correct
what i want is like this
product[0] = {
pname:blah,
pcode:1,
price:5,
detail:blah blah
}
how can i insert values to array in mongoose?
please help me

You have to push the whole object together rather than each field like this -
Store.updateOne({
storenumber: number
}, { $push: { "product": newProduct } }, callback);
and also rather than using callback you should use async await -
module.exports.addProd = async newProd => {
let res = await Store.updateOne({
storenumber: number
}, { $push: { "product": newProduct } });
return res;
}

Iterating through array produced by MongoDB aggregation query

Good afternoon all,
I am having a really tough time working with aggregation queries in MongoDB 3.4. I have a problem that is asking me to do push the results of my aggregation query into an empty array called categories which I have been able to do successfully using this code:
var categories = [];
database.collection("item").aggregate([{
$group : {
_id : "$category",
num : {$sum : 1}
}},
{$sort:{_id:1}}]).toArray(function(err, data){
categories.push(...data);
callback(categories);
console.log(categories);
})
}
categories looks like this:
[ { _id: 'Apparel', num: 6 },
{ _id: 'Books', num: 3 },
{ _id: 'Electronics', num: 3 },
{ _id: 'Kitchen', num: 3 },
{ _id: 'Office', num: 2 },
{ _id: 'Stickers', num: 2 },
{ _id: 'Swag', num: 2 },
{ _id: 'Umbrellas', num: 2 } ]
Next I have the following task:
In addition to the categories created by your aggregation query,
include a document for category "All" in the array of categories
passed to the callback. The "All" category should contain the total
number of items across all categories as its value for "num". The
most efficient way to calculate this value is to iterate through
the array of categories produced by your aggregation query, summing
counts of items in each category.
The problem is that it seems like inside my .toArray() method the data parameter sometimes acts like an array and sometimes not. For example if I wanted to add perhaps just the value of the num key to the categories array like so: categories.push(...data["num"]) I get an error stating undefined is not iterable.
Since I cannot iterate over each data.num key I cannot extract it's value and add it to a running total of all data.num values.
What am I not understanding about what is going on here?

You don't need to use application logic to group data, mongoDB aggregation is made for this task. Add another $group to your query with a new field All that $sum your $num field and $push all documents to a new field called categories :
db.item.aggregate([{
$group: {
_id: "$category",
num: { $sum: 1 }
}
}, { $sort: { _id: 1 } }, {
$group: {
_id: 1,
All: { $sum: "$num" },
categories: {
$push: {
_id: "$_id",
num: "$num"
}
}
}
}])
It gives :
{
"_id": 1,
"All": 23,
"categories": [{
"_id": "Swag",
"num": 2
}, {
"_id": "Office",
"num": 2
}, {
"_id": "Stickers",
"num": 2
}, {
"_id": "Apparel",
"num": 6
}, {
"_id": "Umbrellas",
"num": 2
}, {
"_id": "Kitchen",
"num": 3
}, {
"_id": "Books",
"num": 3
}, {
"_id": "Electronics",
"num": 3
}]
}
For consuming the output, data is an array, to access the first element use data[0] :
var categories = [];
database.collection("item").aggregate([{
$group: {
_id: "$category",
num: { $sum: 1 }
}
}, { $sort: { _id: 1 } }, {
$group: {
_id: 1,
All: { $sum: "$num" },
categories: {
$push: {
_id: "$_id",
num: "$num"
}
}
}
}]).toArray(function(err, data) {
var totalCount = data[0]["All"];
console.log("total count is " + totalCount);
categories = data[0]["categories"];
for (var i = 0; i < categories.length; i++) {
console.log("category : " + categories[i]._id + " | count : " + categories[i].num);
}
})

What I wanted to achieve was pushing or unshifting as we'll see in a moment an object that looked like this into my categories array:
var allCategory = {
_id: "All",
num: [sum of all data.num values]
}
I ended up messing with .reduce() method and used it on the categories array. I got lucky through some console.log-ing and ended up making this:
var categories = [];
database.collection("item").aggregate([{
$group : {
_id : "$category",
num : {$sum : 1}
}},
{$sort:{_id:1}}]).toArray(function(err, data){
categories.push(...data);
var sum = categories.reduce(function(acc, val){
// console.log(acc, val["num"])
return acc + val["num"]
},0);
var allCategory = {
_id: "All",
num: sum
}
categories.unshift(allCategory)
callback(categories);
})
First I use a spread operator to push all the objects from data into categories. Then declare sum which runs .reduce() on categories returning the accumulation of val["num"] which is really data.num (console log is life). I create the allCategory document/object then use .unshift to place it at the beginning of my categories array (this placement was a requirement) then use my callback.
I think it's a hacky way of accomplishing my goal and I had to go through some trial and error as to the correct order of methods and variables in my .toArray(). Yet it worked and I learned something. Thanks for the help #Bertrand Martel .