Data structure design for fast queries MongoDB

Question

I have several collections: photos, photos_like , photos_comment

I have two data structure options:

Case 1: photos_like, photos_comment is a filed array in photos collection

Case 2: use relation to connect between collections

Which option should I use to get the fastest performance?

What are the queries you use most commonly to query photos, photos_like, photos_comment. — Alok Swain, Aug 19 '19 at 05:49
Example: I need to query count(like), count(comment) of photo. — diepnt, Aug 19 '19 at 05:59

score 0 · Answer 1 · answered Aug 19 '19 at 18:41

You should go for case 2 - document reference.

If you start to get a lot of traffic, you will end up having photo documents with hundreds or even thousands of comments and likes inside.

You would have a data structure like:

collection: photos

{
    "_id": ObjectId("5c53653451154c6da4623a79"),
    "name": "ocean",
    "path": "path/to/ocean.png"
}

collection: photo_comments

{
    "_id": ObjectId("c73h42h3ch238c7238cyn34y"),
    "comment": "it's actually a lake",
    "photo": ObjectId("5c53653451154c6da4623a79"),
    "user": ObjectId("sd686sd8ywh3rkjiusyyrk32")
}

collection: photo_likes

{
    "_id": ObjectId("x267cb623yru2ru6c4r273bn"),
    "photo": ObjectId("5c53653451154c6da4623a79"),
    "user": ObjectId("sd686sd8ywh3rkjiusyyrk32")
}

You can get more details at Model One-to-Many Relationships with Document References.

Thank you. I decided to choose case 1 after reading this article: https://stackoverflow.com/questions/5373198/mongodb-relationships-embed-or-reference — diepnt, Aug 21 '19 at 01:02

Data structure design for fast queries MongoDB

1 Answers1