How can I count the number of completed houses designed by a specific architect in MongoDB?
I have the next two collections, "plans" and "houses".
Where the only relationship between houses and plans is that houses have the id of a given plan.
Is there a way to do this in MongoDB with just one query?
plans
{
_id: ObjectId("6388024d0dfd27246fb47a5f")
"hight": 10,
"arquitec": "Aneesa Wade",
},
{
_id: ObjectId("1188024d0dfd27246fb4711f")
"hight": 50,
"arquitec": "Smith Stone",
}
houses
{
_id: ObjectId
"plansId": "6388024d0dfd27246fb47a5f" -> string,
"status": "under construction",
},
{
_id: ObjectId
"plansId": "6388024d0dfd27246fb47a5f" -> string,
"status": "completed",
}
What I tried was to use mongo aggregations while using $match and $lookup.
The "idea" with clear errors would be something like this.
db.houses.aggregate([
{"$match": {"status": "completed"}},
{
"$lookup": {
"from": "plans",
"pipeline": [
{
"$match": {
"$expr": {
"$and": [
{ "$eq": [ "houses.plansId", { "$toString": "$plans._id" }]},
{ "plans.arquitec" : "Smith Stone" },
]
}
}
},
],
}
}
If it's a single join condition, simply do a project to object ID to avoid any complicated lookup pipelines.
Example playground - https://mongoplayground.net/p/gaqxZ7SzDTg
db.houses.aggregate([
{
$match: {
status: "completed"
}
},
{
$project: {
_id: 1,
plansId: 1,
status: 1,
plans_id: {
$toObjectId: "$plansId"
}
}
},
{
$lookup: {
from: "plans",
localField: "plans_id",
foreignField: "_id",
as: "plan"
}
},
{
$project: {
_id: 1,
plansId: 1,
status: 1,
plan: {
$first: "$plan"
}
}
},
{
$match: {
"plan.arquitec": "Some One"
}
}
])
Update: As per OP comment, added additional match stage for filtering the final result based on the lookup response.
Related
In below example, looking for new partner suggestions for user abc. abc has already sent a request to 123 so that can be ignored. rrr has sent request to abc but rrr is in the fromUser field so rrr is still a valid row to be shown as suggestion to abc
I have two collections:
User collection
[
{
_id: "abc",
name: "abc",
group: 1
},
{
_id: "xyz",
name: "xyyy",
group: 1
},
{
_id: "123",
name: "yyy",
group: 1
},
{
_id: "rrr",
name: "tttt",
group: 1
},
{
_id: "eee",
name: "uuu",
group: 1
}
]
Partnership collection (if users have already partnered)
[
{
_id: "abc_123",
fromUser: "abc",
toUser: "123"
},
{
_id: "rrr_abc",
fromUser: "rrr",
toUser: "abc"
},
{
_id: "xyz_rrr",
fromUser: "xyz",
toUser: "rrr"
}
]
My query below excludes the user rrr but it should not because its not listed in toUser field in the partnership collection corresponding to the user abc.
How to modify this query to include user rrr in this case?
db.users.aggregate([
{
$match: {
group: 1,
_id: {
$ne: "abc"
}
}
},
{
$lookup: {
from: "partnership",
let: {
userId: "$_id"
},
as: "prob",
pipeline: [
{
$set: {
users: [
"$fromUser",
"$toUser"
],
u: "$$userId"
}
},
{
$match: {
$expr: {
$and: [
{
$in: [
"$$userId",
"$users"
]
},
{
$in: [
"abc",
"$users"
]
}
]
}
}
}
]
}
},
{
$match: {
"prob.0": {
$exists: false
}
}
},
{
$sample: {
size: 1
}
},
{
$unset: "prob"
}
])
https://mongoplayground.net/p/utGMeHFRGmt
Your current query does not allow creating an existing connection regardless of the connection direction. If the order of the connection is important use:
db.users.aggregate([
{$match: {
group: 1,
_id: {$ne: "abc"}
}
},
{$lookup: {
from: "partnership",
let: { userId: {$concat: ["abc", "_", "$_id"]}},
as: "prob",
pipeline: [{$match: {$expr: {$eq: ["$_id", "$$userId"]}}}]
}
},
{$match: {"prob.0": {$exists: false}}},
{$sample: {size: 1}},
{$unset: "prob"}
])
See how it works on the playground example
For MongoDB 5 and later, I'd propose the following aggregation pipeline:
db.users.aggregate([
{
$match: {
group: 1,
_id: {
$ne: "abc"
}
}
},
{
$lookup: {
from: "partnership",
as: "prob",
localField: "_id",
foreignField: "toUser",
pipeline: [
{
$match: {
fromUser: "abc",
}
}
]
}
},
{
$match: {
"prob.0": {
$exists: false
}
}
},
{
$unset: "prob"
}
])
The following documents are returned (full result without the $sample stage):
[
{
"_id": "eee",
"group": 1,
"name": "uuu"
},
{
"_id": "rrr",
"group": 1,
"name": "tttt"
},
{
"_id": "xyz",
"group": 1,
"name": "xyyy"
}
]
The main difference is that the lookup connects the collections by the toUser field (see localField, foreignField) and uses a minimal pipeline to restrict the results further to only retrieve the requests from the current user document to "abc".
See this playground to test.
When using MongoDB < 5, you cannot use localField and foreignField to run the pipeline only on a subset of the documents in the * from*
collection. To overcome this, you can use this aggregation pipeline:
db.users.aggregate([
{
$match: {
group: 1,
_id: {
$ne: "abc"
}
}
},
{
$lookup: {
from: "partnership",
as: "prob",
let: {
userId: "$_id"
},
pipeline: [
{
$match: {
$expr: {
$and: [
{
$eq: [
"$fromUser",
"abc"
]
},
{
$eq: [
"$toUser",
"$$userId"
]
}
]
}
}
}
]
}
},
{
$match: {
"prob.0": {
$exists: false
}
}
},
{
$unset: "prob"
}
])
The results are the same as for the upper pipeline.
See this playground to test.
For another, another way, this query starts from the partnership collection, finds which users to exclude, and then does a "$lookup" for everybody else. The remainder is just output formatting, although it looks like you may want to add a "$sample" stage at the end.
db.partnership.aggregate([
{
"$match": {
"fromUser": "abc"
}
},
{
"$group": {
"_id": null,
"exclude": {"$push": "$toUser" }
}
},
{
"$lookup": {
"from": "users",
"let": {
"exclude": {"$concatArrays": [["abc"], "$exclude"]
}
},
"pipeline": [
{
"$match": {
"$expr": {
"$not": {"$in": ["$_id", "$$exclude"]}
}
}
}
],
"as": "output"
}
},
{
"$project": {
"_id": 0,
"output": 1
}
},
{"$unwind": "$output"},
{"$replaceWith": "$output"}
])
Try it on mongoplayground.net.
Let's say I have these two collections:
// Members:
{
"_id":{
"$oid":"60dca71f0394f430c8ca296d"
},
"church":"60dbb265a75a610d90b45c6b",
"name":"Julio Verne Cerqueira"
},
{
"_id":{
"$oid":"60dca71f0394f430c8ca29a8"
},
"nome":"Ryan Steel Oliveira",
"church":"60dbb265a75a610d90b45c6c"
}
And
// Churches
{
"_id": {
"$oid": "60dbb265a75a610d90b45c6c"
},
"name": "Saint Antoine Hill",
"active": true
},
{
"_id": {
"$oid": "60dbb265a75a610d90b45c6b"
},
"name": "Jackeline Hill",
"active": true
}
And I want to query it and have a result like this:
// Member with Church names
{
"_id":{
"$oid":"60dca71f0394f430c8ca296d"
},
"church":"Jackeline Hill",
"name":"Julio Verne Cerqueira"
},
{
"_id":{
"$oid":"60dca71f0394f430c8ca29a8"
},
"church":"Saint Antoine Hill",
"nome":"Ryan Steel Oliveira"
}
If I try a Lookup, I have the following Result: (It is getting the entire churches collection).
How would I do the query, so it gives me only the one church that member is related to?
And, if possible, how to Sort the result in alphabetical order by church then by name?
Obs.: MongoDB Version: 4.4.10
There is matching error in the $lookup --> $pipeline --> $match.
It should be:
$match: {
$expr: {
$eq: [
"$_id",
"$$searchId"
]
}
}
From the provided documents, members to churchies relationship will be 1 to many. Hence, when you join members with churchies via $lookup, the output church will be an array with only one churchies document.
Aggregation pipelines:
$lookup - Join members collection (by $$searchId) with churchies (by _id).
$unwind - Deconstruct church array field to multiple documents.
$project - Decorate output document.
$sort - Sort by church and name ascending.
db.members.aggregate([
{
"$lookup": {
"from": "churchies",
"let": {
searchId: {
"$toObjectId": "$church"
}
},
"pipeline": [
{
$match: {
$expr: {
$eq: [
"$_id",
"$$searchId"
]
}
}
},
{
$project: {
name: 1
}
}
],
"as": "church"
}
},
{
"$unwind": "$church"
},
{
$project: {
_id: 1,
church: "$church.name",
name: 1
}
},
{
"$sort": {
"church": 1,
"name": 1
}
}
])
Sample Mongo Playground
I'm doing a $lookup from an _id in Order schema, and its working as expected. But in $project how to add remaining keys. I have added my code below.
Product Collection:
{
"_id": "54759eb3c090d83494e2d804",
"product_name": "sample product",
"image": "default.png",
"price": 55,
"discount": 5,
}
Order list Collection
{
"user_name": "sample1",
"product_list":[
{
"product_id": "54759eb3c090d83494e2d804"
"quantity": 5
}
]
}
lookups
[
{
from: 'product',
localField: 'product_list.product_id',
foreignField: '_id',
as: 'product_list.product_id',
model: 'ProductModel',
},
],
$Project
{
user_name: true,
product_list: {
$map: {
input: '$product_list.product_id',
as: 'product',
in: {
product_name: '$$product.product_name',
},
},
},
}
Current Result:
{
"user_name": "sample1",
"product_list":[
"product_id":{
"product_name": "sample product"
}
]
}
In this current result, the quantity field is missing. How to add in $project?. The expected result shown below
Expected Result:
{
"user_name": "sample1",
"product_list":[
{
"product_id": {
"product_name": "sample product"
}
"quantity": 5
}
]
}
You need to do $unwind before $lookup, because it will not work directly in array fields, and here you don't need $map inside $project,
$unwind product_list deconstruct array
db.order.aggregate([
{ $unwind: "$product_list" },
$lookup with pipeline, this will allow to use pipeline inside lookup, here $project to required fields
{
$lookup: {
from: "product",
as: "product_list.product_id",
let: { product_id: "$product_list.product_id" },
pipeline: [
{
$match: {
$expr: { $eq: ["$$product_id", "$_id"] }
}
},
{
$project: {
_id: 0,
product_name: 1
}
}
]
}
},
$unwind with path product_list.product_id because you need it as object
{ $unwind: { path: "$product_list.product_id" } },
$group by _id re-construct your product_list array
{
$group: {
_id: "$_id",
user_name: { $first: "$user_name" },
product_list: { $push: "$product_list" }
}
}
])
Playground
Can we multiple two different fields from different collections in mongoDB?
any help will be highly appreciated...
Yes, you can using the Aggregation Pipeline $multiply operator. https://docs.mongodb.com/manual/reference/operator/aggregation/multiply/
What you want to do is join two collections together using $lookup https://docs.mongodb.com/manual/reference/operator/aggregation/lookup/. In this case, I'll join the accounts and transactions collections on the account_id field.
Then we can project the fields we want to multiply. In this case, I'm getting the first element in the account array, which represents the account document I'm joining from the accounts collection.
Finally, I can multiply the two fields together.
[{
$lookup: {
from: 'accounts',
localField: 'account_id',
foreignField: 'account_id',
as: 'account'
}
}, {
$project: {
account: {
$arrayElemAt: ["$account", 0]
},
transaction_count: "$transaction_count",
}
}, {
$project: {
product: {
$multiply: ["$transaction_count", "$account.limit"]
}
}
}]
To reproduce my solution above, create a free cluster in Atlas (https://www.mongodb.com/cloud/atlas) and then load the sample data. Navigate to the Cluster's Collections. Then navigate to the sample_analytics database and the transactions collection. Then navigate to the Aggregation tab. Here you can create an Aggregation Pipeline stage by stage. It's incredibly helpful so you can see the output of each stage as you build the next. Below is a screenshot of the Aggregation Pipeline I described in my solution above.
If you don't have experience with the Aggregation Pipeline, I highly recommend MongoDB University's free course: https://university.mongodb.com/courses/M121/about
MongoDB aggregation operations allows us join two collections with $lookup method and compute field operation (i.e $multiply)
Given
"collection": [
{
id: 1,
"total": 5
},
{
id: 2,
"total": 2
}
],
"collection2": [
{
collId: 1,
"total": 3
},
{
collId: 2,
"total": 4
}
]
db.collection.aggregate([
{
$lookup: {
from: "collection2",
let: {
col_id: "$id",
col_total: "$total",
},
pipeline: [
{
$match: {
$expr: {
$eq: [
"$collId",
"$$col_id"
]
}
}
},
{
$project: {
summary: {
$multiply: [
"$total",
"$$col_total"
]
}
}
}
],
as: "result"
}
},
{
$addFields: {
result: {
$let: {
vars: {
tmp: {
$arrayElemAt: [
"$result",
0
]
}
},
in: "$$tmp.summary"
}
}
}
}
])
MongoPlayground
Result
[
{
"_id": ObjectId("5a934e000102030405000000"),
"id": 1,
"result": 15,
"total": 5
},
{
"_id": ObjectId("5a934e000102030405000001"),
"id": 2,
"result": 8,
"total": 2
}
]
This is locations collection data.
{
_id: "1",
location: "loc1",
sublocations: [
{
_id: 2,
sublocation: "subloc1",
},
{
_id: 3,
sublocation: "subloc2",
}
]
},
{
_id: "4",
location: "loc2",
sublocations: [
{
_id: 5,
sublocation: "subloc1",
},
{
_id: 6,
sublocation: "subloc2",
}
]
}
This is products collection data
{
_id: "1",
product: "product1",
prices: [
{
_id: 2,
sublocationid: 2, //ObjectId of object in sublocations array
price: 500
},
{
_id: 3,
sublocationid: 5, //ObjectId of object in sublocations array
price: 200
}
]
}
Now I need to get the sublocation in product schema in the prices array. Expected result is as below.
{
_id: "1",
product: "product1",
prices: [
{
_id: 2,
sublocationid: 3,
sublocation: "subloc2",
price: 500
},
{
_id: 3,
sublocationid: 5,
sublocation: "subloc1"
price: 200
}
]
}
To achieve it, I did it like in the following way.
First, performing aggregation on locations collection - $unwind the sublocations array and store the $out in the new collection.
Second, perform aggregation on 'products' collection - $unwind the prices, $lookup the sublocationid from the new collection and $group them.
Third, after getting data delete the data of new collection.
Is there any other simplified way? Please let me know if there is any.
If you want to stick with 3.4 version, you can try this query:
db.products.aggregate([
{
$unwind: {
"path": "$prices"
}
},
{
$lookup: {
"from": "locations",
"localField": "prices.sublocationid",
"foreignField": "sublocations._id",
"as": "locations"
}
},
{
$unwind: {
"path": "$locations"
}
},
{
$unwind: {
"path": "$locations.sublocations"
}
},
{
$addFields: {
"keep": {
"$eq": [
"$prices.sublocationid",
"$locations.sublocations._id"
]
}
}
},
{
$match: {
"keep": true
}
},
{
$addFields: {
"price": {
"_id": "$prices._id",
"sublocationid": "$prices.sublocationid",
"sublocation": "$locations.sublocations.sublocation",
"price": "$prices.price"
}
}
},
{
$group: {
"_id": "$_id",
"product": { "$first": "$product" },
"prices": { "$addToSet": "$price" }
}
}
]);
It's not as nice as 3.6 version though, because of a higher memory consumption.
You can try below aggregation query in 3.6 version.
Since both local field and foreign field are array you have to $unwind both to do equality comparison.
For this you will have to use new $lookup syntax.
$match with $expr provides comparsion between document fields to look up the location's sublocation document for each product's sublocation id.
$project to project the matching sublocation doc.
$addFields with $arrayElemAt to convert the looked up sublocation array into a document.
$group to push all prices with matching sublocation's document for each product.
db.products.aggregate[
{
"$unwind": "$prices"
},
{
"$lookup": {
"from": "locations",
"let": {
"prices": "$prices"
},
"pipeline": [
{
"$unwind": "$sublocations"
},
{
"$match": {
"$expr": [
"$$prices.sublocationid",
"$sublocations._id"
]
}
},
{
"$project": {
"sublocations": 1,
"_id": 0
}
}
],
"as": "prices.sublocations"
}
},
{
"$addFields": {
"prices.sublocations": {
"$arrayElemAt": [
"$prices.sublocations",
0
]
}
}
},
{
"$group": {
"_id": "$_id",
"product": {
"$first": "$product"
},
"prices": {
"$push": "$prices"
}
}
}
])