I have a working query below:
{
$lookup: {
from: "watchList",
as: "watchList",
let: {
postId: "$_id",
userId: userCurrent
},
pipeline: [
{
$match: {
$and: [
{ $expr: {$eq: ["$postId","$$postId"]} },
{ $expr: {$eq: ["$$userId", "$user"]} },
]
}
},
{
$count: "watchCount"
},
]
}
},
The above query gives me a count of two conditions combined in AND:
{ $expr: {$eq: ["$postId","$$postId"]} },
{ $expr: {$eq: ["$$userId", "$user"]} },
In addition, is it possible to get the count of ONLY { $expr: {$eq: ["$postId","$$postId"]} } without doing another lookup ?
So there will be two counts -
Count 1:
AND condition for
{ $expr: {$eq: ["$postId","$$postId"]} },
{ $expr: {$eq: ["$$userId", "$user"]} },
Count 2:
Single condition
{ $expr: {$eq: ["$postId","$$postId"]} }
You can do something like this,
$group first match count to firstCount and second match count to secondCount
{
$lookup: {
from: "watchList",
as: "watchList",
let: {
postId: "$_id",
userId: userCurrent
},
pipeline: [
{
$group: {
_id: null,
firstCount: {
$sum: {
$cond: [
{
$and: [
{ $eq: ["$postId", "$$postId"] },
{ $eq: ["$$userId", "$user"] }
]
},
1,
0
]
}
},
secondCount: {
$sum: {
$cond: [{ $eq: ["$postId", "$$postId"] }, 1, 0]
}
}
}
}
]
}
}
Related
How to perform multiple let and as and use them within the same pipeline. I have the following query but assignment defaults to userTo. Both userFrom and userTo are from users collection
{
$lookup: {
from: "users",
let: {
userFrom: "$from",
},
as: "userFrom",
let: {
userTo: "$to",
},
as: "userTo",
pipeline: [
{
$match: {
$expr: {
$or: [
{
$eq: [
"$$userFrom",
"$_id"
]
},
{
$eq: [
"$$userTo",
"$_id"
]
}
]
}
}
},
You are not using them correctly. as specifies the name of the output array of the $lookup. There is only 1 result set per lookup so only 1 as would be needed.
let specifies the variables you want to use in the sub-pipeline. You can put them in an object if you want to use multiple variables.
Your code should look like this:
db.collection.aggregate([
{
$lookup: {
from: "users",
let: {
userFrom: "$from",
userTo: "$to"
},
pipeline: [
{
$match: {
$expr: {
$or: [
{
$eq: [
"$$userFrom",
"$_id"
]
},
{
$eq: [
"$$userTo",
"$_id"
]
}
]
}
}
}
],
as: "userLookup"
}
}
])
I need to join two collection with two conditions.
products:
{
...
sku: "4234",
organizationId: ObjectId("asdasdasd);
...
};
order_history:
{
...
itemSku: "4234",
organizationId: ObjectId("asdasdasd);
...
}
I chose pipeline approach:
$lookup: {
from: 'order_history',
let: { foreign_sku: "$itemSku", foreign_organizationId: "$organizationId" },
pipeline: [
{
$match: {
$expr: {
$and: [
{ $eq: ["$organizationId", "$$foreign_organizationId"] },
{ $eq: ["$sku", "$$foreign_sku" ] }
]
}
}
}
],
as: 'order_history'
}
I wrote it on base of Mongo Documentation, but my conditions are ignored.
I have scalar multiplication in result. Where is my mistake?
I already mention in the comment and the code is below
db.products.aggregate([
{
$lookup: {
from: "order_history",
let: {
foreign_sku: "$sku",
foreign_organizationId: "$organizationId"
},
pipeline: [
{
$match: {
$expr: {
$and: [
{
$eq: [
"$organizationId",
"$$foreign_organizationId"
]
},
{
$eq: [
"$itemSku",
"$$foreign_sku"
]
}
]
}
}
}
],
as: "order_history"
}
}
])
Working Mongo playground
when I am running code from Mongodb docs to use pipeline in the $lookup
I am getting an error that let is not supported. How to use let: { <var_1>: , …, <var_n>: } inside of $lookup.
Error:
Code:
db.orders.aggregate([
{
$lookup:
{
from: "warehouses",
let: { order_item: "$item", order_qty: "$ordered" },
pipeline: [
{ $match:
{ $expr:
{ $and:
[
{ $eq: [ "$stock_item", "$$order_item" ] },
{ $gte: [ "$instock", "$$order_qty" ] }
]
}
}
},
{ $project: { stock_item: 0, _id: 0 } }
],
as: "stockdata"
}
}
])
How to transform the data using $if $else groupby condition MongoDB?
This playground should return two object who belongs to text with "tester 2" and "tester 3" also if I have multiple object in history collection it should also check with last object not will all object how it is possible
So condition should say if history's date is $gt then main collection should return nothing else return the matched criteria data.
db.main.aggregate([
{
$lookup: {
from: "history",
localField: "history_id",
foreignField: "history_id",
as: "History"
}
},
{
$unwind: "$History"
},
{
"$match": {
$expr: {
$cond: {
if: {
$eq: [
"5e4e74eb380054797d9db623",
"$History.user_id"
]
},
then: {
$and: [
{
$gt: [
"$date",
"$History.date"
]
},
{
$eq: [
"5e4e74eb380054797d9db623",
"$History.user_id"
]
}
]
},
else: {}
}
}
}
}
])
MongoPlayground
If I understand you correctly, it is what you are trying to do:
db.main.aggregate([
{
$lookup: {
from: "history",
let: {
main_history_id: "$history_id",
main_user_id: { $toString: "$sender_id" }
},
pipeline: [
{
$match: {
$expr: {
$and: [
{
$eq: [
"$history_id",
"$$main_history_id"
]
},
{
$eq: [
"$user_id",
"$$main_user_id"
]
}
]
}
}
}
],
as: "History"
}
},
{
$unwind: {
path: "$History",
preserveNullAndEmptyArrays: true
}
},
{
$sort: {
_id: 1,
"History.history_id": 1,
"History.date": 1
}
},
{
$group: {
_id: "$_id",
data: { $last: "$$ROOT" },
History: { $last: "$History" }
}
},
{
$replaceRoot: {
newRoot: {
$mergeObjects: [
"$data",
{ History: "$History" }
]
}
}
},
{
"$match": {
$expr: {
$or: [
{
$eq: [
{ $type: "$History.date" },
"missing"
]
},
{
$ne: [
"5e4e74eb380054797d9db623",
"$History.user_id"
]
},
{
$and: [
{
$eq: [
"5e4e74eb380054797d9db623",
"$History.user_id"
]
},
{
$gte: [
"$date",
"$History.date"
]
}
]
}
]
}
}
}
])
MongoPlayground
See my condition does work fine for my history's first collection but for second it does not work either If I replace my specified id with 5e4a8d2d3952132a08ae5724 that exists in my second object of history's collection return me all data which is not correct because it's date is greater then main collection's date so it should return me nothing please suggest how to fix it.
db.main.aggregate([
{
$lookup: {
from: "history",
localField: "history_id",
foreignField: "history_id",
as: "History"
}
},
{
$unwind: "$History"
},
{
"$match": {
$expr: {
$cond: {
if: {
$eq: [
"5e4a8d2d3952132a08ae5764",
"$History.user_id"
]
},
then: {
$and: [
{
$gt: [
"$date",
"$History.date"
]
},
{
$eq: [
"5e4a8d2d3952132a08ae5764",
"$History.user_id"
]
}
]
},
else: {}
}
}
}
}
])
when I put two object into history collection it does not work either MongoPlayground
Here is working playground with single history object https://mongoplayground.net/p/hrNofrq1c3S
The reason, why your query (which is posted in the OP) is not working because, you have not specified anything in else part. So, the better approach will be with '$filter' operator.
You can try the below:
db.main.aggregate([
{
$lookup: {
from: "history",
localField: "history_id",
foreignField: "history_id",
as: "History"
}
},
{
$project: {
"History": {
$filter: {
input: "$History",
as: "his",
cond: {
$and: [
{
$lt: [
"$$his.date",
"$date"
]
},
{
$eq: [
"5e4a8d2d3952132a08ae5764",
"$$his.user_id"
]
}
]
}
}
},
data: 1,
history_id: 1,
sender_id: 1,
text: 1,
date: 1
}
},
{
$unwind: "$History"
}
])
MongoPlayGroundLink