What is the difference between the two?
Subcollections store extra data inside a document as a collection and are not part of the document because they must be accessed as a separate call.
Mongodb sub documents store extra documents inside a document property as array and I'm not sure if the whole documents are retrieved in one document call.
Actually, what I'm asking is: How to achieve Subcollections in mongodb?
Related
I was making a commenting system on my website. I stored all the comment data in MongoDB and now I abviously need to access that data to print out the comments to a user. But, I see that there is no 'findMany' function for the collection object. I just need to get all the code in the collection in an array. findOne finds one document, then findMany should be there right? Is there any other such function in the collection object which can give me all the data in a collection of a database in MongoDB
Any help would be great!
You must use the find().toArray() method instead of findMany({ }) to get all the data there in the collection and to keep that data in an array. This will give you an array with all the data in the collection.
I am making an Admin dashboard. I want to show all user's details and their orders. When I want to fetch all documents inside the user collection its returning empty. For more In user collection, each document has some sub-collection. In the account sub-collection, there is a document exists with name details where user account details are available as shown in snapshots.
My code is
export function getUsers() {
return firebase.firestore().collection("users").get();
}
If you store user's details directly in the document instead of 'account' sub-collection then fetching "users" collection will return all users' documents with their data. If you say there's no reason then I'd recommend doing this.
Other option would be to use collectionGroup query on "account" which will fetch all the documents from sub-collections named as "account" i.e. giving you every user's account details.
const snap = await db.collectionGroup('account').get()
const users = snap.docs.map(d => ({id: doc.ref.parent.parent.id, data: d.data()))
Here, id is user's document ID.
Firestore queries only access a single collection, or all collections with a specific name. There is no way to query a collection based on values in another collection.
The most common options are:
Query the parent collection first, then check the subcollection for each document. This approach works best if you have relatively few false positives in the parent collection.
Query all child collections with a collection group query, then check the parent document for each result. This approach works best if you have relatively few false positive in your child collection query.
Replicate the relevant information from the child documents into the parent document, and then query the parent collection based on that. For example, you could add a hasOrders field or an orderCount in the user document. This approach always gives optimal results while querying, but requires that you modify the code that writes the data to accommodate.
The third approach is typically the best for a scalable solution. If you come from a background in relation databases, this sort of data duplication may seen unnatural, but it is actually very common in NoSQL databases where you often have to change your data model to allow the queries your app needs.
To learn more about this, I recommend reading NoSQL data modeling and watching Getting to know Cloud Firestore.
I have a collection in mongoDB that hold 66000 documents on it, Now I want to add new filed to all theses document a uniqueID field which take this form S-1111 and the number increase for the next document
I have tried to make a call to DB and update each one in order but it take to much time because this is a lot of request to mongoDB , so is there is another way to do that fast
I am working with Node and mongoose
I would like to delete all documents in all MongoDB collections. Is there a way to delete all documents in all collections.
I was using db.collection.remove({}) but it only removes all documents in one collection. Is there any command to do? I'm using NodeJS mostly, maybe there is a chance to use NodeJS to delete all documents in all collections?
Sorry if the question is dumb, just started working in MongoDB.
As already suggested - You can either use .dropDatabase() to drop entire database or .collection.drop() to drop a collection or if it's just to delete all documents in all collections then you need to iterate on list of collections and implement either .collection.remove() or .collection.deleteMany() or .findAndModify() without any filter in query condition.
To delete documents in each collection individually :
first list all collection names using .getCollectionNames() and then remove documents.
let colls = db.getCollectionNames() // Mongo shell can accept .Js Func's, if you've more collections you can use parallel as well
colls.forEach(eachColl => db[eachColl].remove({})) // or .deleteMany() or . findAndModify()
Doing this way, you'll still have the database and empty collections existing on MongoDB server. Maybe you can comeback after sometime check list of collections available or maybe rename few etc.
But if you just simply don't want to look at collection names that use to exist in any near future, go ahead with drop commands preferable drop database as you wanted to delete all docs from all collections - why it's preferred ? is because unlike SQL databases MongoDB automatically creates a database and a collection if you write a document for the first time to a collection in a DB. So in MongoDB you might not need to maintain databases with empty collections.
Assume you're querying on collection named girlfriend which is in mylife database - Let's say it's already deleted/missing/never existed then .find() would return [] empty array same like querying on empty collection on a DB - this is the advantage with MongoDB as it doesn't throw an error on mismatched names.
Let's say I have a document with the name "Example123123". I don't know exactly in which collection/subcollection this document is.
How do I search within a collection and its subcollections to find this document and then delete it using Python?
Do I actually have to loop through my collections and subcollections to delete this document?
If you don't know the full path of a document (including all of its collections and nested subcollections), and you aren't able to come up with a query to find it, you will have to list and iterate collections deeply in order to build possible paths to find it and delete it.