Develop Reference

Dynamo DB: How to update specific object inside an array in aws dynamodb?

Inside my companies table there is a company collection I have an array of users.
I need to change one of the users name ('David' to 'Solomon').
I don't mind changing to insert a new user object instead David.
But I don't mind to keep the same id and just change the name field from 'David' to 'Solomon'
company: {
id: cde9e41d-8d16-4054-907f-cc92a69d68e0
name: 'Gold Crowns Ltd',
users: [
{
id: abc9e41d-8d16-4054-907f-cc92a69d68e0
name: 'David' // <-------- I want to change 'David' to 'Solomon'
},
{
id: fgh9e41d-8d16-4054-907f-cc92a69d68e0
name: 'Saul'
},
],
}
Which option will work best and what should be the query in DynamoDB

Create Sequelize Query, Multiple Innerjoins and Wheres across multiple tables

I have created a successful mysql query that joins 2 tables that have foreign keys to each other. I got almost everything to work in Sequelize other than getting the user attached to the responses. My query does that successfully but I cannot understand how to get it.
This is my mysql query that works specifically gets the "users" that has the same id as the response "user_id"
SELECT *
FROM meetup_db.posts p
INNER JOIN meetup_db.responses r
INNER JOIN meetup_db.users u
WHERE p.id = r.post_id AND
r.user_id = u.id
This is my sequelize query that almost works but does not give me back the user in each response where user_id = id
const dbPostData = await Posts.findOne({
where: { id: req.params.id },
include: [
{ model: Users },
{
model: Responses,
include: {
model: Users,
where: { id: Responses.user_id }, //this is the line in question i need the user that has the same id as the Response.user_id
}
}
]
});
The sequelize correctlys outputs everything but the user, heres a sample output as you can see the response has Users listed inside but the users just show as [Object]
{
id: 1,
title: 'BBQ At My House!!',
description: 'Hey gang! Im having a BBQ at my house! I hope all can attend!!',
upvotes: 44,
location: '2113 Main St. Austin, TX.',
date_occuring: 2021-08-04T18:00:00.000Z,
created_at: 2021-08-06T04:42:01.000Z,
edited: false,
user_id: 1,
createdAt: 2021-08-06T04:42:01.000Z,
updatedAt: 2021-08-06T04:42:01.000Z,
User: {
id: 1,
username: 'Jennifer Wylan',
email: 'jwylan#gmail.com',
password: 'ewfchijwnsj',
image_url: '/assets/fake-pfp/fakeperson1.png'
},
Responses: [
{
id: 4,
response: 'Im in there like swimwear!',
user_id: 4,
post_id: 1,
createdAt: 2021-08-06T04:42:01.000Z,
updatedAt: 2021-08-06T04:42:01.000Z,
User: [Object] //these lines right here need to look like the above User: {} Object
},
{
id: 5,
response: 'weeeeeeeeeeeeeeeeeeeeeeeeeeeeee',
user_id: 1,
post_id: 1,
createdAt: 2021-08-06T04:42:01.000Z,
updatedAt: 2021-08-06T04:42:01.000Z,
User: [Object] //these lines right here need to look like the above User: {} Object
}
],
}

I figured it out. So it worked already.
In my terminal the output of responses was showing the User key as [Object]
... Turns out when its like 3 tables deep the terminal just shows [Object] but it was actually there already, you also dont need the where: because it already looks for the foreign key

How do I add a new Subdocument if it's not exist already, then push another subdocument under it

I have a Schema named user on mongoose, and that schema has lastExams property as below:
lastExams: [{
lecture: {
type: String,
required: true
},
exams: [{
examID: {type: [mongoose.Schema.Types.ObjectId], ref: Exam, required: true},
resultID: {type: [mongoose.Schema.Types.ObjectId], ref: Result, required: true},
date: {type: Date, required: true},
result: {}
}]}]
With this, I want to keep the last 10 exams user have taken for each lecture they have. So after each exam, I want to check if the corresponding 'lastExams.lecture' subdocument already exists, if so, push the result that lastExams.$.exams array. Else, upsert that subdocument with first element of the exams array.
for example, thats an user document without any exams on it;
user: {
name: { firstName: '***', lastName: '***' },
email: '****#****.***',
photo: 'https://****.jpg',
role: 0,
status: true,
program: {
_id: 6017b829c878b5bf117dfb92,
dID: '***',
eID: '****',
pID: '****',
programName: '****',
__v: 0
},
lectures: [
{
some data
}
],
currentExams: [
some data
],
lastExams: []
}}
If user sends an exam data for math-1 lecture, since there is no exam with that lecture name, I need to upsert that document to get user document to become as below;
user: {
name: {
firstName: '***',
lastName: '***'
},
email: '****#****.***',
photo: 'https://****.jpg',
role: 0,
status: true,
program: {
_id: 6017 b829c878b5bf117dfb92,
dID: '***',
eID: '****',
pID: '****',
programName: '****',
__v: 0
},
lectures: [{
some data
}],
currentExams: [
some data
],
lastExams: [{
lecture: 'math-1',
exams: [
examID: 601 ba71e62c3d45a4f10f080,
resultID: '602c09b2148214693694b16c',
date: 2021 - 02 - 16 T18: 06: 42.559 Z,
result: {
corrects: 11,
wrongs: 9,
empties: 0,
net: 8.75,
score: 43.75,
qLite: [
'some question objects'
]
}
]
}]
}
}
I can do that like this;
User.findOneAndUpdate({email: result.user}, {$addToSet: {'lastExams': {
lecture: result.lecture,
exams: [{
examID: doc.examID, // btw, idk why, these id's saving to database as arrays
resultID: doc.id,
date: doc.createdAt,
result: doc.results
}]
}}})
But since this adds new subdoc with same lecture value each time. I am having to check if there is a subdoc with that lecture value first manually. if not so, run the above code, else, to push just exam data to that lectures subdoc, I am using below code;
User.findOneAndUpdate({email: result.user, 'lastExams.lecture': result.lecture }, {$addToSet: {'lastExams.$.exams': {
examID: doc.examID,
resultID: doc.id,
date: doc.createdAt,
result: doc.results
}}})
So, I am having to make User.find() query first to see if that lecture is already there, and pop an item if it's exams.lengt is 10. then deciding to what kind of User.findOneAndUpdate() to use.
Do you think there is any way to make this proccess in a single query? Without going to database 2-3 times for each exam save?
I know it's too long, but i couldn't put it straight with my poor english. Sorry.

Two methods:
Like you already did, multiple queries.
In the first query, you have to check if the subdocument exists, if it does, update it in the second query, else create subdocument with first item in the second query.
Using $out in an aggregation pipeline
If multiple round trips is only the issue, checkout $out aggregation pipeline method, which allows to write aggregation output to a collection. In there, you can first match you document, check if the subdocument exists, using $filter followed by $cond. Once you have the data ready, use $out to write it back to the collection.
NB: Aggregation pipeline is expensive operation than findOneAndUpdate IMO, so make sure you test the average latency for both 2 query method and single aggregation method and decide which is faster in your case.
PS: Sorry for not providing an example, I simply don't know it very well to create a working example for you. You can refer to the mongoDB docs for details.
https://docs.mongodb.com/manual/reference/operator/aggregation/out/
Also, there is a Jira ticket discussion going on for this specific use case in MongoDB. Hoping some simple solution will be implemented in MongoDB in the upcoming versions

Mongoose updateMany, but each one with different value

I've got a collection where I put all the users, it has fields like id, name, password, balance, etc. Then in code, I have an array with ids and balance changes. What I want to do is to update balance of all these users with these ids by the amount given in the array.
For example:
Three documents in database:
1. id: 1,
name: John,
balance: 0
2. id: 2,
name: Alice,
balance: 100
3. id: 3,
name: Alex,
balance: 1000
Array:
[
{id: 1, balanceChange: 150},
{id: 3, balanceChange: -500}
]
Would result in John having balance of 150 and Alex 500. I thought about async series and findOneAndUpdate, but I don't know if so many requests are not too heavy. Maybe it is possible to do it in one? Pass an array?
Thanks in advance

MongoDB: projection to match multiple

I am having a bit of trouble here. So I want to show a user's profile. The user belongs to groups. The logged in user can see details of any groups they have in common. Here is some example data
{
_id: "1234",
battletag: "Fake#1234",
guilds: [{
name: "Lok'Narosh!",
rank: 4,
roles: ['casual']
}, {
name: "Warlords of Draenor",
rank: 2,
roles: ['PvP', 'raider']
}, {
name: "Lok'Tar Ogar!",
rank: 3,
roles: ['raider']
}],
}
I can get the current user's groups and reduce it to ['Lok'Narosh!', 'Warlords of Draenor'], meaning that Lok'tar Ogar should be omitted from the results.
The main problem I am coming across is that most operations I know only return the first result. For example, with $elemMatch:
The $elemMatch operator limits the contents of an field from the query results to contain only the first element matching the $elemMatch condition.
Is there a way that I can filter this list to contain all matching elements against a list of elements?

You can use aggregate:
$unwind operator to deconstruct 'guilds' field.
Apply criteria with $match
Reconstruct array.
db.getCollection('yourColl').aggregate({$unwind:"$guilds"},{$match:{"guilds.rank":{$gte:2.0}}},{$group:{ "_id":"$_id", "battletag":{$first:"$battletag"},"guilds":{$addToSet:"$guilds"}}})