I have an object that has an array of page objects and each page object has an array of questions.
Ex object:
{
Id: 1,
UserId: 14,
Deleted: false,
Collaborators: [],
Title: "Awesome",
Pages: [{
Id: 1,
Title: 'Jank',
Questions: [
{ Id: 1, Content: 'Ask me about it' },
{ Id: 2, Content: 'Ask me about it again' }
]
}, {
Id: 2,
Title: 'Janker',
Questions: [
{ Id: 1, Content: 'Tell me about it' },
{ Id: 2, Content: 'Tell me about it again' }
]
}]
}
What I am trying to do is to get a count of all the questions for the entire bas object. I am not sure how to do that. I have tried to use aggregate and $sum the total questions and then do another function to $sum those all together to get a total for the entire object. Unfortunately my $sum is not working like I thought it would.
Ex code (nodejs):
var getQuestionCount = function(id) {
var cursor = mongo.collection('surveys').aggregate([{
$match: {
$or: [{
"UserId": id
}, {
"Collaborators": {
$in: [id]
}
}]
}
}, {
$match: {
"Deleted": false
}
}, {
$unwind: "$Pages"
},
{ $group: { _id: null, number: { $sum: "$Pages.Questions" } } }
], function(err, result) {
//This log just gives me [object Object], [object Object]
console.log('q count ' + result);
});
}
Any idea how to do this? My end result from the example object above would ideally return 4 as the question count for the whole object.
I'd try following shell query.
db.collection.aggregate([
// filter out unwanted documents.
{$match:{Id: 1}},
// Unwind Pages collection to access Questions array
{$unwind:"$Pages"},
// Count items in Questions array
{$project:{count: {$size:"$Pages.Questions"}}},
// Finally sum items previously counted.
{$group:{_id:"$_id", total: {$sum: "$count"}}}
])
Based on your sample document, it should return correct count of Questions.
{
"_id" : ObjectId("57723bb8c10c41c41ff4897c"),
"total" : NumberInt(4)
}
Related
I have a database of a the employees of a company that looks like this:
{
_id: 7698,
name: 'Blake',
job: 'manager',
manager: 7839,
hired: ISODate("1981-05-01T00:00:00.000Z"),
salary: 2850,
department: {name: 'Sales', location: 'Chicago'},
missions: [
{company: 'Mac Donald', location: 'Chicago'},
{company: 'IBM', location: 'Chicago'}
]
}
I have an exercise in which I need to write the MongoDb command that returns all them employees who did all their missions in Chicago. I struggle with the all because I cannot find a way to check that all the locations of the missions array are equal to 'Chicago'.
I was thinking about doing it in two time: first find the total number of missions the employee has and then compare it to the number of mission he has in Chicago (that how I would do in SQL I guess). But I cannot found the number of mission the employee did in Chicago. Here is what I tried:
db.employees.aggregate([
{
$match: { "missions": { $exists: true } }
},
{
$project: {
name: 1,
nbMissionsChicago: {
$sum: {
$cond: [
{
$eq: [{
$getField: {
field: { $literal: "$location" },
input: "$missions"
}
}, "Chicago"]
}, 1, 0
]
}
}
}
}
])
Here is the result :
{ _id: 7698, name: 'Blake', nbMissionsChicago: 0 }
{ _id: 7782, name: 'Clark', nbMissionsChicago: 0 }
{ _id: 8000, name: 'Smith', nbMissionsChicago: 0 }
{ _id: 7902, name: 'Ford', nbMissionsChicago: 0 }
{ _id: 7499, name: 'Allen', nbMissionsChicago: 0 }
{ _id: 7654, name: 'Martin', nbMissionsChicago: 0 }
{ _id: 7900, name: 'James', nbMissionsChicago: 0 }
{ _id: 7369, name: 'Smith', nbMissionsChicago: 0 }
First of all, is there a better method to check that all the locations of the missions array respect the condition? And why does this commands returns only 0 ?
Thanks!
If all you need is the agents who had all their missions in "Chicago" then you don't need an aggregation pipeline for it, specifically the approach of filtering the array as part of the aggregation can't utilize an index and will make performance even worse.
A simple query should suffice here:
db.collection.find({
$and: [
{
"missions": {
$exists: true
}
},
{
"missions.location": {
$not: {
$gt: "Chicago"
}
}
},
{
"missions.location": {
$not: {
$lt: "Chicago"
}
}
}
]
})
Mongo Playground
This way we can build an index on the missions field and utilize it properly, any documents with a different value other then "Chigaco" will not match as they will fail the $gt or $lt comparion.
Note that an empty array also matches the condition, you can change the generic "missions" exists condition key into "missions.0": {$exists: true}, this will also require at least one mission.
You are unable to get the correct result as it is not the correct way to iterate the element in an array field.
Instead, you need to work with $size operator to get the size of an array and the $filter operator to filter the document.
Updated: You can directly compare the filtered array with the original array.
db.employees.aggregate([
{
$match: {
"missions": {
$exists: true
}
}
},
{
$project: {
name: 1,
nbMissionsChicago: {
$eq: [
{
$filter: {
input: "$missions",
cond: {
$eq: [
"$$this.location",
"Chicago"
]
}
}
},
"$missions"
]
}
}
}
])
Demo # Mongo Playground
I'm starting to learn Aggregate in MongoDB. I have a simple Doc as below, which has 2 fields, name and examScores, examScores is an array contains multiplier documents:
{ _id: ObjectId("633199db009be219a43ae426"),
name: 'Max',
examScores:
[ { difficulty: 4, score: 57.9 },
{ difficulty: 6, score: 62.1 },
{ difficulty: 3, score: 88.5 } ] }
{ _id: ObjectId("633199db009be219a43ae427"),
name: 'Manu',
examScores:
[ { difficulty: 7, score: 52.1 },
{ difficulty: 2, score: 74.3 },
{ difficulty: 5, score: 53.1 } ] }
Now I query the maximum score of each person using $unwind and $group/$max as below:
db.test.aggregate([
{$unwind: "$examScores"},
{$group: {_id: {name: "$name"}, maxScore: {$max: "$examScores.score"}}}
])
{ _id: { name: 'Max' }, maxScore: 88.5 }
{ _id: { name: 'Manu' }, maxScore: 74.3 }
But I want the result also contains the examScores.difficulty field corresponding to name and examScores.score, like below:
{ _id: { name: 'Max' }, difficulty: 3, maxScore: 88.5 }
{ _id: { name: 'Manu' }, difficulty: 2, maxScore: 74.3 }
I know that I can use $sort + $group and $first to achieve this goal. But I want to use $getField or any other methods to get data from ROOT Doc.
My idea is use $project and $getField to get the difficulty field from ROOT doc (or $unwind version of ROOT doc) with the condition like ROOT.name = Aggregate.name and Root.examScores.score = Aggregate.maxScore.
It will look something like this:
{$project:
{name: 1,
maxScore: 1,
difficulty:
{$getField: {
field: "$examScores.difficulty"
input: "$$ROOT.$unwind() with condition/filter"}
}
}
}
I wonder if this is possible in MongoDB?
Solution 1
$unwind
$group - Group by name. You need $push to add the $$ROOT document into data array.
$project - Set the difficulty field by getting the value of examScores.difficulty from the first item of the filtered data array by matching the examScores.score with maxScore.
db.collection.aggregate([
{
$unwind: "$examScores"
},
{
$group: {
_id: {
name: "$name"
},
maxScore: {
$max: "$examScores.score"
},
data: {
$push: "$$ROOT"
}
}
},
{
$project: {
_id: 0,
name: "$_id.name",
maxScore: 1,
difficulty: {
$getField: {
field: "difficulty",
input: {
$getField: {
field: "examScores",
input: {
$first: {
$filter: {
input: "$data",
cond: {
$eq: [
"$$this.examScores.score",
"$maxScore"
]
}
}
}
}
}
}
}
}
}
}
])
Demo Solution 1 # Mongo Playground
Solution 2: $rank
$unwind
$rank - Ranking by partition name and sort examScores.score descending.
$match - Filter the document with { rank: 1 }.
$unset - Remove rank field.
db.collection.aggregate([
{
$unwind: "$examScores"
},
{
$setWindowFields: {
partitionBy: "$name",
sortBy: {
"examScores.score": -1
},
output: {
rank: {
$rank: {}
}
}
}
},
{
$match: {
rank: 1
}
},
{
$unset: "rank"
}
])
Demo Solution 2 # Mongo Playground
Opinion: I would say this approach:
$sort by examScores.score descending
$group by name, take the first document
would be much easier.
There's no need to $unwind and then rebuild the documents again via $group to achieve your desired results. I'd recommend avoiding that altogether.
Instead, consider processing the arrays inline using array expression operators. Depending on the version and exact results you are looking for, here are two starting points that may be worth considering. In particular the $maxN operator and the $sortArray operator may be of interest for this particular question.
You can get a sense for what these two operators do by running an $addFields aggregation to see their output, playground here.
With those as a starting point, it's really up to you to make the pipeline output the desired result. Here is one such example that matches the output you described in the question pretty well (playground):
db.collection.aggregate([
{
"$addFields": {
"relevantEntry": {
$first: {
$sortArray: {
input: "$examScores",
sortBy: {
"score": -1
}
}
}
}
},
},
{
"$project": {
_id: 0,
name: 1,
difficulty: "$relevantEntry.difficulty",
maxScore: "$relevantEntry.score"
}
}
])
Which yields:
[
{
"difficulty": 3,
"maxScore": 88.5,
"name": "Max"
},
{
"difficulty": 2,
"maxScore": 74.3,
"name": "Manu"
}
]
Also worth noting that this particular approach doesn't do anything special if there are duplicates. You could look into using $filter if something more was needed in that regard.
I have the following schema into my DB:
{ name: 'AFG',
documents: [
{ name: 'doc1',
templates: [
{ name: 'templ1',
lastModified: <Date>},
...]
},
...]
}
I am trying to make a query to look for the template with name 'templ1'. If I find it, I have to compare the last modification date with another and update the value. If I don't find it, I have to push it into the array.
I have tried to do it with the following query:
Country.findOne({name : countrySelected, documents : {$elemMatch: {name: documentSelected}}, 'documents.templates' : {$elemMatch: {name: templateSelected}}}, function(err, templateFound){...}
But I get the following error:
MongoError: cannot use the part (documents of documents.templates) to traverse the element ({documents: [ { name: "Passport", templates: [] }, { name: "Visa", templates: [] }, { name: "Driver's Licence", templates: [] }, { name: "Id Card", templates: [] }, { name: "Other", templates: [] } ]})
Someone knows how can I do it? Thanks!!
You have to use the $in operator to search in arrays.
Country.findOne({
name : countrySelected,
documents: {
$elemMatch: {
$and: [{
name: {
$in: documentSelected //<-- must be array like ['doc1']
}
}, {
'templates.name': {
$in: documentSelected //<-- must be array like ['tmpl1']
}
}]
}
}
}, function(err, templateFound){
//do something with err and templateFound
});
To update the LastModified date you need to update it in the callback function and save the document.
See this answer for nested array updates
I have a Model in MongoDB which include an array(category) which has an array(picture) inside it.
Shirt Model looks like this:
{ _id: 100, category: [ { name: 'CatName', _id: 101, picture: [Object] } ] }
And my Picture Array looks like this:
[ { path: 'p1', _id: 102 },
{ path: 'p2', _id: 103 } ] }
I Pass 3 variables
main array id which is 100 (var1)
category name which is CatName (var2)
picture id which is 102 (var3)
I want to GET an array which looks like:
{ _id: 100, category: [ { name: 'CatName', _id: 101,
picture: [ { path: 'p1', _id: 102 }]
} ]
}
What I have tried is this:
Shirt.find( {_id: var1} ,
{category: { $and:[ { name: var2 } , { picture: {$elemMatch: {_id: var3}}} ] }} )
.exec(function(err, product) {
console.log('Result ' + product );
res.jsonp(product);
});
But the Result I receive is Undefined for First Code
Second Code That I tried:
Shirt.find( {_id: var1} ,
{category: {$elemMatch: { name: var2,picture: {$elemMatch: {_id: var3} }}} } )
And Result from second code filter the array for var1 and var2
But it contain the whole picture array which means it does not filter var3
What is the correct code to find what I want?
Is this a correct approach for a Shopping Website database Or you have a better suggestion?
Am I applying Parent and Child Database Correctly?
Thanks!
Following mongo query will give you expected result:
db.collection.find({
"category": {
$elemMatch: {
"name": "CatName",
"picture": {
$elemMatch: {
"_id": 102
}
}
}
}
})
You need to convert it in node.js format.
Following format may help you. Not Tested
collection.find({
_id: "" // add your match Id here} ,
{
category: {
"$elemMatch": {
"name": "CatName",
"picture": {
$elemMatch: {
"_id": 102
}
}
}
}
}
})
.exec(function(err, product) {
console.log('Result ' + product);
res.jsonp(product);
});
AFTER EDIT QUESTION
You should use mongo aggregation to get required values. Query will be like following -
db.collection.aggregate({
$unwind: '$category'
}, {
$unwind: '$category.picture'
}, {
$match: {
_id: 100, // add here your var1 variable instead of 100
'category.name': 'CatName', // add here your var2 variable instead of 'CatName'
'category._id': 102, //add your match id here if any otherwise remove this condition
'category.picture._id': 102 //add your var3 instead of 102
}
}, {
$group: {
_id: '$category.name',
'name': {
$first: '$category.name'
},
'picture': {
'$push': '$category.picture'
}
}
})
Lets say that I have the following document in the books collection:
{
_id:0 ,
item: "TBD",
stock: 0,
info: { publisher: "1111", pages: 430 },
tags: [ "technology", "computer" ],
ratings: [ { _id:id1, by: "ijk", rating: 4 }, {_id:id2 by: "lmn", rating: 5 } ],
reorder: false
}
I would like to update the value of ratings[k].rating and all I know is the id of the collection and the _id of the objects existing in the array ratings.
The tutorial of mongoDB has the following example that uses the position of the object inside the array but I suppose that if the update can only be done by knowing the position, this means that I firstly have to find the position and then proceed with the update? Can I do the update with only one call and if so how I can do that?
db.books.update(
{ _id: 1 },
{
$inc: { stock: 5 },
$set: {
item: "ABC123",
"info.publisher": "2222",
tags: [ "software" ],
"ratings.1": { by: "xyz", rating: 3 }
}
}
)
Sorry for late answer; I think this is what you want to do with mongoose.
Books.findOneAndUpdate({
_id: 1,
'ratings._id': id1
},
{
$set: {
'ratings.$.rating' : 3
}
}, function(err, book){
// Response
});
Positional operator may help you:
db.books.update(
// find book by `book_id` with `rating_id` specified
{ "_id": book_id, "ratings._id": rating_id },
// set new `value` for that rating
{ $set: { 'ratings.$.rating': value }}
);
$ will save position of matched document.