I would like to build a search function with several different filters. I have a RangeSlider component and function that give me the respective min max values. I save these filter values as objects and send them to the backend immediately each time a filter is changed.
Here I work with if, else conditions, which is certainly not the right way, but I didn't know what else to do and wanted to have at least a working prototype.
If you have one or two filters, this can still work, but not if you have many different ones. Furthermore, I wonder how to optimise the whole filtering process? With every request, the entire collection is searched. It would be great if the previous search query is applied to each new filter instead of searching through the entire collection again.
How can this be achieved?
Frontend
Every time a filter is updated activeFilters will be sent to the backend
const activeFilters = reactive({ salePrice: '', space: '' })
async function updateFilter(minmax, property) {
activeFilters[property] = minmax
const filteredObjects = await $fetch('/api/properties/filtered', {
method: 'POST',
body: activeFilters,
})
return filteredObjects
}
Backend
body = { "salePrice": { "min": 630000, "max": 850948 }, "space": { "min": 53, "max": 167 } }
export default defineEventHandler(async (event) => {
const body = await readBody(event)
try {
if (body.salePrice !== '' && body.space !== '') {
const properties = await Property.find({
salePrice: { $gte: body.salePrice.min, $lte: body.salePrice.max },
livableSurface: { $gte: body.space.min, $lte: body.space.max },
})
return properties
}
if (body.salePrice !== '') {
const properties = await Property.find({
salePrice: { $gte: body.salePrice.min, $lte: body.salePrice.max },
})
return properties
}
if (body.space !== '') {
const properties = await Property.find({
livableSurface: { $gte: body.space.min, $lte: body.space.max },
})
return properties
}
const properties = await Property.find()
return properties
} catch (err) {
console.dir(err)
event.res.statusCode = 500
return {
code: 'ERROR',
message: 'Something went wrong.',
}
}
})
Html
<InputsRangeSlider
:config="salePriceSliderConfig"
#updated-min-max="updateFilter($event, 'salePrice')"
/>
<InputsRangeSlider
:config="spaceSliderConfig"
#updated-min-max="updateFilter($event, 'space')"
/>
Maybe something like this?
const {salePrice, space} = body;
const conditions = {};
if (salePrice) conditions.salePrice = {$gte: salePrice.min, $lte: salePrice.max};
if (space) conditions.livableSurface = {$gte: space.min, $lte: space.max};
return Property.find(conditions);
I just want to change the value of a key of all the objects inside an array
What I want actually -
The object which I queried from the database is -
{
_id: 61389277fa5c742caf959885,
title: 'What is GRE?',
forumTab: 'GRE',
askedAt: 2021-09-08T10:37:43.979Z,
askedBy: {
_id: 60f0a6a9b4259f7ef9c49cc8,
}
}
I want to add more key-value pairs in the askedBy key by again querying the database for the User with the given _id
Now, the user object which is queried is -
{
role: 'student',
_id: 60f0a6a9b4259f7ef9c49cc8,
firstName: 'Rishav',
lastName: 'Raj'
}
Finally I want to return the below object in response -
{
_id: 61389277fa5c742caf959885,
title: 'What is GRE?',
forumTab: 'GRE',
askedAt: 2021-09-08T10:37:43.979Z,
askedBy: {
_id: 60f0a6a9b4259f7ef9c49cc8,
role: 'student',
firstName: 'Rishav',
lastName: 'Raj'
}
}
I am creating a new array questionsToSend and pushing the object with updated key-value pairs which I am getting after querying the database for each elements in the questions array, I have created functions for respective query that I need to render in sequence, even after rendering the functions in proper sequence why the new array questionsToSend is not populating with the objects before returning the response?
router.get("/questions", async (req, res) => {
if (!req.query.forumTab) return res.status(400).send("something went wrong");
const page = parseInt(req.query.page) - 1;
const perPage = parseInt(req.query.perPage);
let questionsToSend = [];
const func0 = async (callback) => {
const questions = await Question.find({ forumTab: req.query.forumTab })
.sort({ askedAt: -1 })
.limit(perPage)
.skip(perPage * page);
console.log("xxxxxxx");
callback(questions);
};
const func1 = async (questions, callBack) => {
questions.forEach(async (question) => {
const askedUserData = await User.findById(question.askedBy._id);
if (!askedUserData) {
const index = questions.indexOf(question);
questions.splice(index, 1);
return;
}
questionsToSend.push({
..._.pick(question, [
"_id",
"title",
"askedAt",
"tags",
]),
askedUserData,
});
console.log(questionsToSend);
});
console.log("yyyyyyyy");
callBack();
};
func0(
(questions) =>
func1(questions, async () => {
console.log("zzzzzzzz");
res.status(200).send(questionsToSend);
})
);
});
We can use aggregation to achieve this
Question.aggregate([
{
$match: { forumTab: req.query.forumTab }
},
{
$lookup: {
from: 'users',
localField: 'askedBy._id',
foreignField: '_id',
as: "user"
}
},
{ $unwind: "$user"},
{ "$addFields": {
"askedBy": {
"$mergeObjects": ["$askedBy", "$user"]
}
}
},
{ $project: { "user" : 0} },
{ $sort: {"askedAt": -1}},
{ $skip: perPage * page},
{ $limit: perPage},
])
$match is used to apply filter
$lookup is used to do a join on a collection. I have assumed the collection name is users.
$lookup returns the matched result as an array. Converting it to object using $unwind since we get only one back.
$addFields with $mergeObjects is merging the existing askedBy field and newly user field
Removing the user field from the result set with $project.
And then sort, skip and limit.
I want to update a field in my MongoDB database with Mongoose if the new value of that field wouldn't be greater than another field. Here is my code:
Training.findOneAndUpdate(
{ date: dateStringForDB, startHour: retrievedRequest.body.trainingStartHour },
{ $push: { participants: retrievedRequest.session.loggedInPhoneNumber }, $inc: { currentQuota: +1 } },
(err, doc, updateResponse) => {
if (err) {
console.log("Error while updating training ", err);
return;
}
retrievedResponse.redirect("/schedule");
}
);
What I want to do is increment the value of currentQuota only if value of 'currentQuota' is smaller than another field's (initialQuota) value. Is there a way to do it with findOneAndUpdate method or shall I call find method first and then update?
Thanks in advance!
You can compare two fields within the same document using $expr in your query object.
Training.findOneAndUpdate(
{ date: dateStringForDB, startHour: retrievedRequest.body.trainingStartHour, $expr: { $gt:["$initialQuota", "$currentQuota"] } },
{ $push: { participants: retrievedRequest.session.loggedInPhoneNumber }, $inc: { currentQuota: +1 } },
(err, doc, updateResponse) => {
if (err) {
console.log("Error while updating training ", err);
return;
}
retrievedResponse.redirect("/schedule");
}
);
Refer to this for more info:
MongoDb query condition on comparing 2 fields
Mongodb docs: https://docs.mongodb.com/manual/reference/operator/query/expr/
I have 2 dates; sales_date (When the service was sold) and the cancellation_date (When the service was cancelled). I want to calculate the tenure by Month doing a subtraction between cancellation_date - sales_date.
This is the code that I am currently doing:
router.get('/subtract_date', auth, async (req, res) => {
try {
const model_CancellationKPI = await CancellationKPI.aggregate([
{ "$project" : { "difference" : { "$subtract" : ["$cancellation_date", "$sales_date"] } } }
])
res.json(model_CancellationKPI);
} catch (err) {
console.error(err.message);
res.status(500).send('Server Error');
});
And the JSON output is:
{
"_id": "5d30c48e5fbf3c0507250bb5",
"difference": 31536000000
}
I have this JSON: How can I output a JSON displaying the tenure in month (cancellation_date - sales_date) by client_name?
await CancellationKPI.aggregate([
{ "$project" : { "difference" : { "$subtract" : ["$cancellation_date", "$sales_date"] } , $add: [
new Date(0),
"$difference"
] }}
]);
Your query of date difference is working alright , it should give the result in milliseconds all it needs to be converted back to date , checkout toDate aggregation. You can check here for the result of above query
I am interested in optimizing a "pagination" solution I'm working on with MongoDB. My problem is straight forward. I usually limit the number of documents returned using the limit() functionality. This forces me to issue a redundant query without the limit() function in order for me to also capture the total number of documents in the query so I can pass to that to the client letting them know they'll have to issue an additional request(s) to retrieve the rest of the documents.
Is there a way to condense this into 1 query? Get the total number of documents but at the same time only retrieve a subset using limit()? Is there a different way to think about this problem than I am approaching it?
Mongodb 3.4 has introduced $facet aggregation
which processes multiple aggregation pipelines within a single stage
on the same set of input documents.
Using $facet and $group you can find documents with $limit and can get total count.
You can use below aggregation in mongodb 3.4
db.collection.aggregate([
{ "$facet": {
"totalData": [
{ "$match": { }},
{ "$skip": 10 },
{ "$limit": 10 }
],
"totalCount": [
{ "$group": {
"_id": null,
"count": { "$sum": 1 }
}}
]
}}
])
Even you can use $count aggregation which has been introduced in mongodb 3.6.
You can use below aggregation in mongodb 3.6
db.collection.aggregate([
{ "$facet": {
"totalData": [
{ "$match": { }},
{ "$skip": 10 },
{ "$limit": 10 }
],
"totalCount": [
{ "$count": "count" }
]
}}
])
No, there is no other way. Two queries - one for count - one with limit. Or you have to use a different database. Apache Solr for instance works like you want. Every query there is limited and returns totalCount.
MongoDB allows you to use cursor.count() even when you pass limit() or skip().
Lets say you have a db.collection with 10 items.
You can do:
async function getQuery() {
let query = await db.collection.find({}).skip(5).limit(5); // returns last 5 items in db
let countTotal = await query.count() // returns 10-- will not take `skip` or `limit` into consideration
let countWithConstraints = await query.count(true) // returns 5 -- will take into consideration `skip` and `limit`
return { query, countTotal }
}
Here's how to do this with MongoDB 3.4+ (with Mongoose) using $facets. This examples returns a $count based on the documents after they have been matched.
const facetedPipeline = [{
"$match": { "dateCreated": { $gte: new Date('2021-01-01') } },
"$project": { 'exclude.some.field': 0 },
},
{
"$facet": {
"data": [
{ "$skip": 10 },
{ "$limit": 10 }
],
"pagination": [
{ "$count": "total" }
]
}
}
];
const results = await Model.aggregate(facetedPipeline);
This pattern is useful for getting pagination information to return from a REST API.
Reference: MongoDB $facet
Times have changed, and I believe you can achieve what the OP is asking by using aggregation with $sort, $group and $project. For my system, I needed to also grab some user info from my users collection. Hopefully this can answer any questions around that as well. Below is an aggregation pipe. The last three objects (sort, group and project) are what handle getting the total count, then providing pagination capabilities.
db.posts.aggregate([
{ $match: { public: true },
{ $lookup: {
from: 'users',
localField: 'userId',
foreignField: 'userId',
as: 'userInfo'
} },
{ $project: {
postId: 1,
title: 1,
description: 1
updated: 1,
userInfo: {
$let: {
vars: {
firstUser: {
$arrayElemAt: ['$userInfo', 0]
}
},
in: {
username: '$$firstUser.username'
}
}
}
} },
{ $sort: { updated: -1 } },
{ $group: {
_id: null,
postCount: { $sum: 1 },
posts: {
$push: '$$ROOT'
}
} },
{ $project: {
_id: 0,
postCount: 1,
posts: {
$slice: [
'$posts',
currentPage ? (currentPage - 1) * RESULTS_PER_PAGE : 0,
RESULTS_PER_PAGE
]
}
} }
])
there is a way in Mongodb 3.4: $facet
you can do
db.collection.aggregate([
{
$facet: {
data: [{ $match: {} }],
total: { $count: 'total' }
}
}
])
then you will be able to run two aggregate at the same time
By default, the count() method ignores the effects of the
cursor.skip() and cursor.limit() (MongoDB docs)
As the count method excludes the effects of limit and skip, you can use cursor.count() to get the total count
const cursor = await database.collection(collectionName).find(query).skip(offset).limit(limit)
return {
data: await cursor.toArray(),
count: await cursor.count() // this will give count of all the documents before .skip() and limit()
};
It all depends on the pagination experience you need as to whether or not you need to do two queries.
Do you need to list every single page or even a range of pages? Does anyone even go to page 1051 - conceptually what does that actually mean?
Theres been lots of UX on patterns of pagination - Avoid the pains of pagination covers various types of pagination and their scenarios and many don't need a count query to know if theres a next page. For example if you display 10 items on a page and you limit to 13 - you'll know if theres another page..
MongoDB has introduced a new method for getting only the count of the documents matching a given query and it goes as follows:
const result = await db.collection('foo').count({name: 'bar'});
console.log('result:', result) // prints the matching doc count
Recipe for usage in pagination:
const query = {name: 'bar'};
const skip = (pageNo - 1) * pageSize; // assuming pageNo starts from 1
const limit = pageSize;
const [listResult, countResult] = await Promise.all([
db.collection('foo')
.find(query)
.skip(skip)
.limit(limit),
db.collection('foo').count(query)
])
return {
totalCount: countResult,
list: listResult
}
For more details on db.collection.count visit this page
It is possible to get the total result size without the effect of limit() using count() as answered here:
Limiting results in MongoDB but still getting the full count?
According to the documentation you can even control whether limit/pagination is taken into account when calling count():
https://docs.mongodb.com/manual/reference/method/cursor.count/#cursor.count
Edit: in contrast to what is written elsewhere - the docs clearly state that "The operation does not perform the query but instead counts the results that would be returned by the query". Which - from my understanding - means that only one query is executed.
Example:
> db.createCollection("test")
{ "ok" : 1 }
> db.test.insert([{name: "first"}, {name: "second"}, {name: "third"},
{name: "forth"}, {name: "fifth"}])
BulkWriteResult({
"writeErrors" : [ ],
"writeConcernErrors" : [ ],
"nInserted" : 5,
"nUpserted" : 0,
"nMatched" : 0,
"nModified" : 0,
"nRemoved" : 0,
"upserted" : [ ]
})
> db.test.find()
{ "_id" : ObjectId("58ff00918f5e60ff211521c5"), "name" : "first" }
{ "_id" : ObjectId("58ff00918f5e60ff211521c6"), "name" : "second" }
{ "_id" : ObjectId("58ff00918f5e60ff211521c7"), "name" : "third" }
{ "_id" : ObjectId("58ff00918f5e60ff211521c8"), "name" : "forth" }
{ "_id" : ObjectId("58ff00918f5e60ff211521c9"), "name" : "fifth" }
> db.test.count()
5
> var result = db.test.find().limit(3)
> result
{ "_id" : ObjectId("58ff00918f5e60ff211521c5"), "name" : "first" }
{ "_id" : ObjectId("58ff00918f5e60ff211521c6"), "name" : "second" }
{ "_id" : ObjectId("58ff00918f5e60ff211521c7"), "name" : "third" }
> result.count()
5 (total result size of the query without limit)
> result.count(1)
3 (result size with limit(3) taken into account)
Try as bellow:
cursor.count(false, function(err, total){ console.log("total", total) })
core.db.users.find(query, {}, {skip:0, limit:1}, function(err, cursor){
if(err)
return callback(err);
cursor.toArray(function(err, items){
if(err)
return callback(err);
cursor.count(false, function(err, total){
if(err)
return callback(err);
console.log("cursor", total)
callback(null, {items: items, total:total})
})
})
})
Thought of providing a caution while using the aggregate for the pagenation. Its better to use two queries for this if the API is used frequently to fetch data by the users. This is atleast 50 times faster than getting the data using aggregate on a production server when more users are accessing the system online. The aggregate and $facet are more suited for Dashboard , reports and cron jobs that are called less frequently.
We can do it using 2 query.
const limit = parseInt(req.query.limit || 50, 10);
let page = parseInt(req.query.page || 0, 10);
if (page > 0) { page = page - 1}
let doc = await req.db.collection('bookings').find().sort( { _id: -1 }).skip(page).limit(limit).toArray();
let count = await req.db.collection('bookings').find().count();
res.json({data: [...doc], count: count});
I took the two queries approach, and the following code has been taken straight out of a project I'm working on, using MongoDB Atlas and a full-text search index:
return new Promise( async (resolve, reject) => {
try {
const search = {
$search: {
index: 'assets',
compound: {
should: [{
text: {
query: args.phraseToSearch,
path: [
'title', 'note'
]
}
}]
}
}
}
const project = {
$project: {
_id: 0,
id: '$_id',
userId: 1,
title: 1,
note: 1,
score: {
$meta: 'searchScore'
}
}
}
const match = {
$match: {
userId: args.userId
}
}
const skip = {
$skip: args.skip
}
const limit = {
$limit: args.first
}
const group = {
$group: {
_id: null,
count: { $sum: 1 }
}
}
const searchAllAssets = await Models.Assets.schema.aggregate([
search, project, match, skip, limit
])
const [ totalNumberOfAssets ] = await Models.Assets.schema.aggregate([
search, project, match, group
])
return await resolve({
searchAllAssets: searchAllAssets,
totalNumberOfAssets: totalNumberOfAssets.count
})
} catch (exception) {
return reject(new Error(exception))
}
})
I had the same problem and came across this question. The correct solution to this problem is posted here.
You can do this in one query. First you run a count and within that run the limit() function.
In Node.js and Express.js, you will have to use it like this to be able to use the "count" function along with the toArray's "result".
var curFind = db.collection('tasks').find({query});
Then you can run two functions after it like this (one nested in the other)
curFind.count(function (e, count) {
// Use count here
curFind.skip(0).limit(10).toArray(function(err, result) {
// Use result here and count here
});
});