I am working on an aggregate pipeline for MongoDB, and I am trying to retrieve items where the user is not equal to a variable.
For some reason, I couldn't make it work. I tried to use $not, $ne and $nin in different possible way but can't make it to work.
This is how it looks like:
Data sample:
[{
"_id": { "$oid": "565674e2e4b030fba33d8fdc" },
"user": { "$oid": "565674832b85ce78732b7529" }
}, {
"_id": { "$oid": "565674e2e4b030fba33d8fdc" },
"user": { "$oid": "565674832b85ce78732b7529" }
}, {
"_id": { "$oid": "565674e2e4b030fba33d8fdc" },
"user": { "$oid": "56f9dfc5cc03ec883f7675d0" }
}]
Pipeline sample (simplified for this question):
Where req.query.user.id = "565674832b85ce78732b7529"
collection.aggregate([
{
$match: {
user: {
$nin: [ req.query.user.id ],
}
}
}
]
This should return only the last item.
Do you have any idea how to retrieve the data that doesn't match the user?
Thanks
Edit:
The following doesn't work either:
collection.aggregate([
{
$match: {
'user.$oid': {
$nin: [ req.query.user.id ],
}
}
}
]);
I also tried with ObjectID() and mongodb complains: [MongoError: Argument must be a string]
var ObjectID = require('mongodb').ObjectID;
// Waterline syntax here
MyCollection.native(function (err, collection) {
collection.aggregate([
{
$match: {
'user': {
$nin: [ ObjectID(req.query.user.id) ],
}
}
}
], function (err, result) {
console.log(err, result);
});
});
But this line works in the shell:
db.collection.aggregate([{$match:{"user":{"$nin":[ObjectId("565674832b85ce78732b7529")]}}}])
Based on the answer here, you can change
var ObjectId = require('mongodb'). ObjectID;
to
var ObjectId = require('sails-mongo/node_modules/mongodb').ObjectID;
Related
I have a node.js server using express and mongoose and I also have a Json structure of :
[
{
"_id": "63dbaf5daabee478202ae59f",
"experimentId": "85a91abe-ef2f-416f-aa13-ec1bdf5d9766",
"experimentData": [
{
"scanId": 1652890241,
"scanData": [
{
"areaName": "A1",
"areaData": [],
"_id": "63dbaf94aabee478202ae5a5"
},
...
],
"_id": "63dbaf6caabee478202ae5a3"
},
...
],
"__v": 2
},
...
]
How can I create a query to return a single object from the scanData array like
{
"areaName": "A1",
"areaData": [],
"_id": "63dbb006e322869df811eea4"
}
The best I was able to do was:
// * Get all shapes in a well/area
// ! uses the experiment id, scan id and areaName
router.get("/:id/scan/:scanId/area/:areaName", async (req, res) => {
try {
const experiment = await Experiment.findOne({
experimentId: req.params.id,
experimentData: {
$elemMatch: {
scanId: req.params.scanId,
scanData: {
$elemMatch: {
areaName: req.params.areaName
}
}
}
}
}, {'experimentData.scanData.$': 1})
console.log(experiment)
if (!experiment || experiment.length === 0) res.status(404).json({})
else {
res.send(experiment.experimentData[0])
}
} catch (err) {
res.status(500).json({ message: err.message })
}
})
But that just returned the scanData array it would be great if I could go one level deeper and just get the object with the areaName.
I also tried some solutions with $aggregate but was not able to get any data displayed it kept returning an empty array
You can $match by your criteria layer-by-layer and $unwind to get the final scanData object in an aggregation pipeline. Use $replaceRoot to get only the scanData object.
db.collection.aggregate([
{
"$match": {
"experimentId": "85a91abe-ef2f-416f-aa13-ec1bdf5d9766"
}
},
{
"$unwind": "$experimentData"
},
{
"$match": {
"experimentData.scanId": 1652890241
}
},
{
"$unwind": "$experimentData.scanData"
},
{
"$match": {
"experimentData.scanData.areaName": "A1"
}
},
{
"$replaceRoot": {
"newRoot": "$experimentData.scanData"
}
}
])
Mongo Playground
So I'm still new using MongoDB, so what I'm trying to do here is count all category under productId who have same category. So the expected output should be 7. I used populate first but got stuck on how can I use the $count. Instead I use aggregate and then use $lookup, but i only empty array of product
CartSchema.js
const CartSchema = new mongoose.Schema({
productId: {type: mongoose.Schema.Types.ObjectId, ref: 'Product'}
})
export default mongoose.model('Cart', CartSchema)
ProductSchema.js
const ProductSchema = new mongoose.Schema({
category: {type: String, required: true},
})
export default mongoose.model('Product', ProductSchema)
I used this code to show the information under productId.
router.get('/categories', async (req, res) => {
try {
const cart = await Cart.find()
.populate([
{path: 'productId', select: 'category' },
]).exec()
res.status(200).json(cart);
} catch (error) {
res.status(500).json({error: error.message})
}
})
The result of populate method.
[
{
"_id": "63b410fdde61a124ffd95a51",
"productId": {
"_id": "63b410d6de61a124ffd9585b",
"category": "CASE"
},
},
{
"_id": "63b41a679950cb7c5293bf12",
"productId": {
"_id": "63b41637e3957a541eb59e81",
"category": "CASE"
},
},
{
"_id": "63b433ef226742ae6b30b991",
"productId": {
"_id": "63b41637e3957a541eb59e81",
"category": "CASE"
},
},
{
"_id": "63b670dc62b0f91ee4f8fbd9",
"productId": {
"_id": "63b410d6de61a124ffd9585b",
"category": "CASE"
},
},
{
"_id": "63b6710b62b0f91ee4f8fc13",
"productId": {
"_id": "63b410d6de61a124ffd9585b",
"category": "CASE"
},
},
{
"_id": "63b671bc62b0f91ee4f8fc49",
"productId": {
"_id": "63b410d6de61a124ffd9585b",
"category": "CASE"
},
},
{
"_id": "63b6721c62b0f91ee4f8fcc5",
"productId": {
"_id": "63b410d6de61a124ffd9585b",
"category": "CASE"
},
]
So I used this method, but instead, I just get an empty array
router.get('/categories', async (req, res) => {
try {
const cart = await Cart.aggregate([
{
$lookup: {
from: 'product',
localField: 'productId',
foreignField: '_id',
as: 'product'
}
},
{
$unwind: "$product"
},
{
$group: {
_id: "$product.category",
total: {
$sum: 1
}
}
},
{
$sort: {total: -1}
},
{
$project: {
_id: 0,
category: "$_id",
total: 1
}
},
])
res.status(200).json(cart);
} catch (error) {
res.status(500).json({error: error.message})
}
})
In the aggregation, the collection to perform the $lookup on should be products (with an s) rather than product.
The name of the collection that Mongoose creates in your database is the same as the name of your model, except lowercase and pluralized, as documented in the documentation.
Mongoose automatically looks for the plural, lowercased version of your model name. Thus, for the example above, the model Tank is for the tanks collection in the database.
(emphasis theirs)
When using the aggregation framework, your aggregation pipeline is sent to the database as-is. Mongoose doesn't do any sort of coercion or casting on it. So when writing aggregation pipelines you should more or less forget you're using Mongoose. What's important is the name of the underlying collection in Mongo, which is generated from your model name based on the mentioned rule.
You can also override the collection name yourself if desired, for example:
export default mongoose.model('Product', ProductSchema, 'xyz');
This will override Mongoose's default naming behavior and will name the collection xyz.
I would like to find a single document matching the courseID but inside the document only objects from the materials array whose moduleNo matches the one I give. But the query I currently use seems to return the correct document but also returns all the objects in materials array. Any help would be appreciated.
My schema,
const materialSchema = new mongoose.Schema({
courseID: String,
materials: [
{
moduleNo: Number,
moduleMaterial: String,
},
],
});
My code/query,
exports.getMaterials = (req, res) => {
const { courseID, moduleNo } = req.query;
Material.findOne(
{ courseID, "materials.moduleNo": moduleNo },
(err, result) => {
if (err) {
console.error(err);
} else {
res.json(result);
}
}
);
};
Use the $elemMatch operator, something lik this:
exports.getMaterials = (req, res) => {
const { courseID, moduleNo } = req.query;
Material.findOne(
{ courseID },
{"materials": { $elemMatch: {moduleNo: moduleNo}},
(err, result) => {
if (err) {
console.error(err);
} else {
res.json(result);
}
}
);
};
Update: To return all matching elements in the array, you will have to use an aggregation pipeline, having $filter stage, to filter out array elements. Like this:
exports.getMaterials = (req, res) => {
const { courseID, moduleNo } = req.query;
Material.aggregate(
[
{
$match: {
courseID: courseID
}
},
{
"$project": {
courseID: 1,
materials: {
"$filter": {
"input": "$materials",
"as": "material",
"cond": {
"$eq": [
"$$material.moduleNo",
moduleNo
]
}
}
}
}
}
]
);
};
Here's the playground link.
Way 1 : Use $elemMatch operator in project field
The $elemMatch operator limits the contents of an array field from
the query results to contain only the first element matching the
$elemMatch condition
Result : Returns only one matching array element
syntax :
db.collection.find(query,projection)
db.collection.find({
"field": field_value
},{
"array_name":{
$elemMatch:{"key_name": value }
},
field:1,
field_2:1,
field_3:0
})
https://mongoplayground.net/p/HKT1Gop32Pq
Way 2 : Array Field Limitations array.$ in project field
*
Result : Returns only one matching array element
db.collection.find({
"field": field_value,
"array_name.key_name": value
},{
"array_name.$":1,
field:1,
field_2:1,
field_3:0
});
https://mongoplayground.net/p/Db0azCakQg9
Update : Using MongoDB Aggregation
Result : Returns multiple matching array elements
db.collection.aggregate([
{
"$unwind": "$materials"
},
{
"$match": {
"courseID": "Demo",
"materials.moduleNo": 1
}
}
])
will return output as :
[
{
"_id": ObjectId("5a934e000102030405000000"),
"courseID": "Demo",
"materials": {
"moduleMaterial": "A",
"moduleNo": 1
}
},
{
"_id": ObjectId("5a934e000102030405000000"),
"courseID": "Demo",
"materials": {
"moduleMaterial": "B",
"moduleNo": 1
}
}
]
And If you want to format output :
db.collection.aggregate([
{
"$unwind": "$materials"
},
{
"$match": {
"courseID": "Demo",
"materials.moduleNo": 1
}
},
{
"$group": {
"_id": {
"courseID": "$courseID",
"moduleNo": "$materials.moduleNo"
},
"materials": {
"$push": "$materials.moduleMaterial"
}
}
},
{
"$project": {
"_id": 0,
"courseID": "$_id.courseID",
"moduleNo": "$_id.moduleNo",
"materials": "$materials"
}
}
])
will return result as :
[
{
"courseID": "Demo",
"materials": [
"A",
"B"
],
"moduleNo": 1
}
]
https://mongoplayground.net/p/vdPVbce6WkX
I was wondering if it was possible to destructure arrays while I am still in the MongoDB aggregation pipeline which would make my code alot neater.
For example, I have the following aggregation pipeline.
await User.aggregate([
{ $match: { _id: userID } },
{
$project: { chatLogs: 1, username: 1, profilePicURL: 1 },
},
{ $unwind: "$chatLogs" },
{
$lookup: {
from: "users",
let: { recipientID: "$chatLogs.recipientID" },
pipeline: [
{
$match: { $expr: { $eq: ["$_id", "$$recipientID"] } },
},
{ $project: { profilePicURL: 1 } },
],
as: "chatLogs.recipientID",
},
},
]);
This gives the following results when queried:
{
"_id": "5f2ffb54eea9c2180a732afa",
"username": "joe",
"profilePicURL": "/images/profile/default_profile.png",
"chatLogs": {
"recipientID": [
{
"_id": "5f2faf5ad18a76073729f475",
"profilePicURL": "/images/profile/default_profile.png"
}
],
"chat": "5f30b6c3d117441c2abda1ba"
}
}
In my case, because "recipientID" represents a default MongoDB id, it will always be unique. Hence I would prefer the following, where the resulting recipientID field is no longer a meaningless array
Desired results:
{
"_id": "5f2ffb54eea9c2180a732afa",
"username": "joe",
"profilePicURL": "/images/profile/default_profile.png",
"chatLogs": {
"recipientID": {
"_id": "5f2faf5ad18a76073729f475",
"profilePicURL": "/images/profile/default_profile.png"
}
"chat": "5f30b6c3d117441c2abda1ba"
}
}
You can deconstruct recipientID array using $unwind in last pipeline,
await User.aggregate([
... // your all pipelines
// add this line
{ $unwind: "$chatLogs.recipientID" }
]);
I have this document in my database:
{
"_id": "ObjectId(...)",
"chapters": [
{
"_id": "ObjectId(...)",
"link": "128371.html",
"content": ""
}
]
}
The chapters array can have up to 3k items, and I have to populate each content attribute with some info. I want to be able to save the info I want inside the right object. Until now I was able to change the content attribute generally (in all items), but I am having trouble filtering it. This is what I managed to code using what I found in other questions:
let content = "Testing";
await models.ListNovel.updateOne(
{ link: novel_link },
{ $set: { "chapters.$[].content": content } }
);
I saw that { arrayFilters: [{ link: { $eq: chapter_link } }], multi: false } may work in some cases, but I don't use the link identifier in the update.
Thank you!
UPDATE
Similar to Suleyman's solution, I ended up with the following working code, I hope it may be useful for you.
await models.ListNovel.updateOne(
{ link: novel.link },
{ $set: { "chapters.$[elem].content": content } },
{
multi: true,
arrayFilters: [{ "elem.link": { $eq: chapter.link } }]
}
);
The condition in updateOne must match parent object, but you are using { link: novel_link } which belongs to the inner array object field, so it cannot find the document, and update doesn't happen.
To illustrate this, let's say your schema is like this:
const mongoose = require("mongoose");
const schema = new mongoose.Schema({
name: String,
chapters: [
new mongoose.Schema({
link: String,
content: String
})
]
});
module.exports = mongoose.model("ListNovel", schema);
Let's have this existing document in this collection:
{
"_id": "5e498a1fe21eea0e10690e39",
"name": "Novel1",
"chapters": [
{
"_id": "5e498a1fe21eea0e10690e3b",
"link": "128371.html",
"content": ""
},
{
"_id": "5e498a1fe21eea0e10690e3a",
"link": "222222.html",
"content": ""
}
],
"__v": 0
}
If we want to update this document's chapter with "link": "128371.html", first we need to find it with name or _id field, and update it using the filtered positional operator $.
router.put("/novels/:name", async (req, res) => {
const novel_link = "128371.html";
const content = "Testing";
const result = await ListNovel.findOneAndUpdate(
{ name: req.params.name },
{
$set: { "chapters.$[chapter].content": content }
},
{
arrayFilters: [{ "chapter.link": novel_link }],
new: true
}
);
res.send(result);
});
Here I used findOneAndUpdate to immediately retrieve the updated document, but you can also use the updateOne instead of findOneAndUpdate.
The result will be like this:
{
"_id": "5e498a1fe21eea0e10690e39",
"name": "Novel1",
"chapters": [
{
"_id": "5e498a1fe21eea0e10690e3b",
"link": "128371.html",
"content": "Testing" // => UPDATED
},
{
"_id": "5e498a1fe21eea0e10690e3a",
"link": "222222.html",
"content": ""
}
],
"__v": 0
}