Need help with Mongodb best practices

help
1

I need to know what are the best practices for storing data in Mongodb.

I have a scenario where I need to develop a group chat.

Currently I have implemented the following structure:

Collection #1 - Users:

{ _id: "", name: "", email: ""}

Collection #2 - Groups:

{ _id: "", title: "", photo: "", "members": [{userId: ""}, {userId: ""}, {userId: ""}]}

Collection #3 - Messages:

{ _id: "", userId: "", messageText: ""}

I have created 3 different collections for this. Is this a good practice?

Or should I do something like:

Keep only one collection i.e: Users and put Groups and Messages under each user respectively?

Something like this:

{ 
	_id: "", 
	name: "", 
	email: "",
	groups: [
		{ 
			_id: "",
		 	title: "",
		 	photo: "",
		 	members: [{userId: ""}, {userId: ""}, {userId: ""}],
		 	messages: [
		 		{ _id: "", userId: "", messageText: ""},
		 		{ _id: "", userId: "", messageText: ""},
		 		{ _id: "", userId: "", messageText: ""},
		 	]
		},
		{ 
			_id: "",
		 	title: "",
		 	photo: "",
		 	members: [{userId: ""}, {userId: ""}, {userId: ""}],
		 	messages: [
		 		{ _id: "", userId: "", messageText: ""},
		 		{ _id: "", userId: "", messageText: ""},
		 		{ _id: "", userId: "", messageText: ""},
		 	]
		}
	]
}
2

One collection will be a headcahe once your users grows.

3

So do you recommend my original implication for this scenario?

4

I would also suggest using 3 collections instead of a single one. But I would change the structure a little bit:

Users: { _id: “”, name: “”, email: “”, groups: [ groupId0, …, groupIdN ]}
Groups: { _id: “”, title: “”, photo: “” }
Messages: { _id: “”, userId: “”, messageText: “”, groupId: “” }

5

Right. So we all agreed on 3 separate collections.

Now there is a confusing scenario, for “me” atleast:

What If I want to perform a deep search i.e on the groups listing screen, I want to type a keyword: “Mic”.

Now I want to search “Mic” in Groups+Users+Messages, A record from any source is appreciated.

How we handle such scenarios?

6

That’s when we combine them as an index that we push to elasticsearch depending on the needs of the search engine

7

In Atmosphere search for “socialize”. You will find everything there, you can get some inspiration or use as is. From what I see you need the structure of a forum with rooms rather than a chat. If you need a chat that looks like a chat things are far more complex since you might need to do user relationships, “who is typing”, delete a message (for me or everyone), aggregations by user, unread messages (keep track of who red a message in a room/chat).

"members": [{userId: ""}, {userId: ""}, {userId: ""}]

could be an array of user Ids instead of objects and you update it with $addToSet in order to avoid duplicates.
If you may have 100 - 1000 users in a group you should probably not have a members array at all. You could probably do an extra collection such as Conversations or Checkins and keep track of which user is in which Group.
E.g.

{  
   _id: "_"
    userId: "_",
    userName: "_",
    userEmail: "_",
    groupId: "_",
    unreadMessages: "_",
    // etc....
}

Then your group members will be a search in this collection rather than an aggregate between Groups and Users. Keep in mind that on large scale, storage is cheaper than querying in Mongo.