I have model like this:
{
name: 'John Doe',
items: [
{ count: 5, item: ObjectId('xxx1') },
{ count: 2, item: ObjectId('xxx2') }
]
}
items field is not required and contains number field and reference to other entity. I would like to replace item inside items array with data from entity like so:
{
name: 'John Doe',
items: [
{ count: 5, item: { more: 'data', from: 'other entity' } },
{ count: 2, item: { more: 'data 2', from: 'other entity 2' } }
]
}
I tried using mongo's aggregate and lookup:
Model.aggregate([
{
$lookup: {
from: 'items',
localField: 'users.items',
foreignField: '_id',
as: 'users.items'
}
}
]);
but that's replacing everything inside items array (loosing field count). How can I fix it?
Try this one:
db.collection.aggregate([
{ $unwind: { path: "$items", preserveNullAndEmptyArrays: true } },
{
$lookup: {
from: 'items',
localField: 'items.item',
foreignField: '_id',
as: 'items.item'
}
},
{ $set: { "items.item": { $arrayElemAt: ["$items.item", 0] } } },
{
$group: {
_id: { _id: "$_id", name: "$name" },
items: { $push: "$$ROOT.items" }
}
},
{ $replaceRoot: { newRoot: { $mergeObjects: ["$$ROOT", "$_id"] } } }
])
Related
I have documents like this in DB. And I need to grab the data of each item based on the itemType from their own collection.
{ listId: 2, itemType: 'book', itemId: 5364 },
{ listId: 2, itemType: 'car', itemId: 354 },
{ listId: 2, itemType: 'laptop', itemId: 228 }
Based on MongoDB docs and some search, I figured out that I need to use let and $expr in lookup, to make some condition.
ListItemsModel.aggregate([
{ $match: { listId: 2 } },
{ $lookup:
{
from: 'books',
localField: 'itemId',
foreignField: '_id',
let: { "itemType": "$itemType" },
pipeline: [
{ $project: { _id: 1, title: 1 }},
{ $match: { $expr: { $eq: ["$$itemType", "book"] } }}
],
as: 'data'
}
},
{ $lookup:
{
from: 'cars',
localField: 'itemId',
foreignField: '_id',
let: { "itemType": "$itemType" },
pipeline: [
{ $project: { _id: 1, title: 1 }},
{ $match: { $expr: { $eq: ["$$itemType", "car"] } }}
],
as: 'data'
}
},
{ $lookup:
{
from: 'laptops',
localField: 'itemId',
foreignField: '_id',
let: { "itemType": "$itemType" },
pipeline: [
{ $project: { _id: 1, title: 1 }},
{ $match: { $expr: { $eq: ["$$itemType", "laptop"] } }}
],
as: 'data'
}
}
]);
The problem is, in the result all data fields are empty as data: [].
The syntax seems correct to me. What's wrong?
Any subsequent reassignment of field values will eliminate any previous value.
So, for your aggregation pipeline, you need to assign different values to each "$lookup" "as" field.
For example:
// ...
{ $lookup:
{
from: 'books',
// ...
as: 'booksData'
}
},
{ $lookup:
{
from: 'cars',
// ...
as: 'carsData'
}
},
{ $lookup:
{
from: 'laptops',
// ...
as: 'laptopsData'
}
},
// ...
So I have 2 models user & form.
User Schema
firstName: {
type: String,
required: true,
},
lastName: {
type: String,
required: true,
},
email: {
type: String,
required: true,
}
Form Schema
approvalLog: [
{
attachments: {
type: [String],
},
by: {
type: ObjectId,
},
comment: {
type: String,
},
date: {
type: Date,
},
},
],
userId: {
type: ObjectId,
required: true,
},
... other form parameters
When returning a form, I'm trying to aggregate the user info of every user in the approvalLog into their respective objects as below.
{
...other form info
approvalLog: [
{
attachments: [],
_id: '619cc4953de8413b548f61a6',
by: '619cba9cd64af530448b6347',
comment: 'visit store for disburement',
date: '2021-11-23T10:38:13.565Z',
user: {
_id: '619cba9cd64af530448b6347',
firstName: 'admin',
lastName: 'user',
email: 'admin#mail.com',
},
},
{
attachments: [],
_id: '619cc4ec3ea3e940a42b2d01',
by: '619cbd7b3de8413b548f61a0',
comment: '',
date: '2021-11-23T10:39:40.168Z',
user: {
_id: '619cbd7b3de8413b548f61a0',
firstName: 'sam',
lastName: 'ben',
email: 'sb#mail.com',
},
},
{
attachments: [],
_id: '61a9deab8f472c52d8bac095',
by: '61a87fd93dac9b209096ed94',
comment: '',
date: '2021-12-03T09:08:59.479Z',
user: {
_id: '61a87fd93dac9b209096ed94',
firstName: 'john',
lastName: 'doe',
email: 'jd#mail.com',
},
},
],
}
My current code is
Form.aggregate([
{
$lookup: {
from: 'users',
localField: 'approvalLog.by',
foreignField: '_id',
as: 'approvedBy',
},
},
{ $addFields: { 'approvalLog.user': { $arrayElemAt: ['$approvedBy', 0] } } },
])
but it only returns the same user for all objects. How do I attach the matching user for each index?
I've also tried
Form.aggregate([
{
$lookup: {
from: 'users',
localField: 'approvalLog.by',
foreignField: '_id',
as: 'approvedBy',
},
},
{
$addFields: {
approvalLog: {
$map: {
input: { $zip: { inputs: ['$approvalLog', '$approvedBy'] } },
in: { $mergeObjects: '$$this' },
},
},
},
},
])
This adds the right user to their respective objects, but I can only add the to the root object and not a new one.
You can try the approach,
$map to iterate loop of approvalLog
$filter to iterate loop of approvedBy array and search for user id by
$arrayElemAt to get first element from above filtered result
$mergeObjects to merge current object properties of approvalLog and filtered user
$$REMOVE don't need approvedBy now
await Form.aggregate([
{
$lookup: {
from: "users",
localField: "approvalLog.by",
foreignField: "_id",
as: "approvedBy"
}
},
{
$addFields: {
approvalLog: {
$map: {
input: "$approvalLog",
as: "a",
in: {
$mergeObjects: [
"$$a",
{
user: {
$arrayElemAt: [
{
$filter: {
input: "$approvedBy",
cond: { $eq: ["$$a.by", "$$this._id"] }
}
},
0
]
}
}
]
}
}
},
approvedBy: "$$REMOVE"
}
}
])
Playground
The second approach using $unwind,
$unwind deconstruct the approvalLog array
$lookup with user collection
$addFields and $arrayElemAt to get first element from lookup result
$group by _id and reconstruct the approvalLog array and get first value of other required properties
await Form.aggregate([
{ $unwind: "$approvalLog" },
{
$lookup: {
from: "users",
localField: "approvalLog.by",
foreignField: "_id",
as: "approvalLog.user"
}
},
{
$addFields: {
"approvalLog.user": {
$arrayElemAt: ["$approvalLog.user", 0]
}
}
},
{
$group: {
_id: "$_id",
approvalLog: { $push: "$approvalLog" },
userId: { $first: "$userId" },
// add your other properties like userId
}
}
])
Playground
Hello i am trying to join two collections...
#COLLECTION 1
const valuesSchema= new Schema({
value: { type: String },
})
const categoriesSchema = new Schema({
name: { type: String },
values: [valuesSchema]
})
mongoose.model('categories', categoriesSchema )
#COLLECTION 2
const productsSchema = new Schema({
name: { type: String },
description: { type: String },
categories: [{
type: mongoose.Schema.Types.ObjectId,
ref: 'categories',
}]
})
mongoose.model('productos', productsSchema )
Now, what i pretend to do is join these collections and have an output like this.
#Example Product Document
{
name: 'My laptop',
description: 'Very ugly laptop',
categories: ['5f55949054f3f31db0491b5c','5f55949054f3f31db0491b5b'] // these are _id of valuesSchema
}
#Expected Output
{
name: 'My laptop',
description: 'Very ugly laptop',
categories: [{value: 'Laptop'}, {value: 'PC'}]
}
This is what i tried.
{
$lookup: {
from: "categories",
let: { "categories": "$categories" },
as: "categories",
pipeline: [
{
$match: {
$expr: {
$in: [ '$values._id','$$categories']
},
}
},
]
}
}
but this query is not matching... Any help please?
You can try,
$lookup with categories
$unwind deconstruct values array
$match categories id with value id
$project to show required field
db.products.aggregate([
{
$lookup: {
from: "categories",
let: { cat: "$categories" },
as: "categories",
pipeline: [
{ $unwind: "$values" },
{ $match: { $expr: { $in: ["$values._id", "$$cat"] } } },
{
$project: {
_id: 0,
value: "$values.value"
}
}
]
}
}
])
Playground
Since you try to use the non-co-related queries, I appreciate it, you can easily achieve with $unwind to flat the array and then $match. To regroup the array we use $group. The $reduce helps to move on each arrays and store some particular values.
[
{
$lookup: {
from: "categories",
let: {
"categories": "$categories"
},
as: "categories",
pipeline: [
{
$unwind: "$values"
},
{
$match: {
$expr: {
$in: [
"$values._id",
"$$categories"
]
},
}
},
{
$group: {
_id: "$_id",
values: {
$addToSet: "$values"
}
}
}
]
}
},
{
$project: {
categories: {
$reduce: {
input: "$categories",
initialValue: [],
in: {
$concatArrays: [
"$$this.values",
"$$value"
]
}
}
}
}
}
]
Working Mongo template
I'm trying to do a nested population by using the mongodb's aggregation framework and I have some troubles with it.
This is the initial data that I have:
[
{
_id: ObjectId('123'),
profileId: ObjectId('456')
},
// ...other documents
]
I apply this aggregation pipeline to it so I can populate the profile field by using the profileId field:
MyModel.aggregate([
{
$lookup: {
from: 'profiles',
localField: 'profileId',
foreignField: '_id',
as: 'profile'
}
},
{
$project: {
profile: {
$arrayElemAt: [ '$profile', 0 ]
},
profileId: 1,
}
},
]
And this is the result:
[
{
_id: ObjectId('123'),
profileId: ObjectId('456'),
profile: {
grades: [
ObjectId('...'),
ObjectId('...')
]
// ... other props
}
}
// ...other documents
]
Now I expand the pipeline by adding a $lookup to populate the grades inside each profile document:
MyModel.aggregate([
{
$lookup: {
from: 'profiles',
localField: 'profileId',
foreignField: '_id',
as: 'profile'
}
},
{
$project: {
profile: {
$arrayElemAt: [ '$profile', 0 ]
},
profileId: 1,
}
},
{
$lookup: {
from: 'profile-grades',
localField: 'profile._id',
foreignField: 'profile',
as: 'profile.grades'
}
}
]
This is the result so far:
[
{
_id: ObjectId('123'),
profileId: ObjectId('456'),
profile: {
grades: [
{
studyLocationId: ObjectId('789'),
// ... other props
},
// ... other grades
]
}
}
// ...other documents
]
The final step that I'm not able to achieve is the population of each studyLocation inside the grades array.
Wanted result:
[
{
_id: ObjectId('123'),
profileId: ObjectId('456'),
profile: {
grades: [
{
studyLocationId: ObjectId('789'),
studyLocation: {
_id: ObjectId('...'),
// other props
},
},
// ... other grades
]
}
}
// ...
]
I've tried by adding another $lookup stage but without luck:
{
$lookup: {
from: 'study-locations',
localField: 'profile.grades.studyLocationId',
foreignField: '_id',
as: 'profile.grades.studyLocation'
}
}
This simply returns:
grades: {
studyLocation: []
}
How should I do it? Is this even possible?
Thank you!
If you are using mongodb3.4 this will work, for previous versions you need unwind operator on grades.
I want to do a Full Outer Join in MongoDB by lookup mongoDB query. Is this possible? Is a Full Outer Join supported by MongoDB by any other alternative?
[Update:]
I want to achieve result from Collection1 & Collection2 as following attachment:
Example: Result Required
In above result column there may be different arithmetic operations and will be further used in calculations.
You can use $unionWith (starting 4.4)
Something like this:
db.c1.aggregate([
{$set: {
mark1: "$marks"
}},
{$unionWith: {
coll: 'c2',
pipeline: [{$set: {mark2: "$marks"}}]
}},
{$group: {
_id: "$name",
result: {
$sum: "$marks"
},
mark1: {$first: {$ifNull: ["$mark1", 0]}},
mark2: {$first: {$ifNull: ["$mark2", 0]}}
}}])
I have named the collections as coll1 and coll2 then just use this query it will give you the required output.
db.getCollection('coll1').aggregate([
{
$facet: {
commonRecords: [{
$lookup: {
from: "coll2",
localField: 'name',
foreignField: 'name',
as: "coll2"
}
},
{
$unwind: {
path: '$coll2',
preserveNullAndEmptyArrays: true
}
}
]
}
},
{
$lookup: {
from: "coll2",
let: {
names: {
$map: {
input: '$commonRecords',
as: 'commonRecord',
in: '$$commonRecord.name'
}
}
},
pipeline: [{
$match: {
$expr: {
$eq: [{
$indexOfArray: ['$$names', '$name']
}, -1]
}
}
}, ],
as: "coll2"
}
},
{
$addFields: {
coll2: {
$map: {
input: '$coll2',
as: 'doc',
in: {
coll2: '$$doc'
}
}
}
}
},
{
$project: {
records: {
$concatArrays: ['$commonRecords', '$coll2']
}
}
},
{
$unwind: '$records'
},
{
$replaceRoot: {
newRoot: '$records'
}
},
{
$project: {
_id: 0,
name: {
$ifNull: ['$name', '$coll2.name']
},
marks1: {
$ifNull: ['$marks', 0]
},
marks2: {
$ifNull: ['$coll2.marks', 0]
}
}
},
{
$addFields: {
result: {
$add: ['$marks1', '$marks2']
}
}
}
])
This is a sample:
{
$lookup:
{
from: [collection to join],
local_Field: [field from the input documents],
foreign_Field: [field from the documents of the "from" collection],
as: [output field]
}
}
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