Hey! A dumb question about m-n relations with Mongo. The docs say that reference IDs must be present at both sides. But why is that necessary? E.g. imagine

Post.categories

relation. In inverse relation

Category.posts

would explode the

Category

entity, there would be hundreds of thousands of entries in it. Besides, it may eventually lead to inconsistent date if

Post.categories

wouldn’t match

Category.posts

for some reason. So is there a way to only store the relation information on a

Post

side and query things based only on it? An alternative would be to get rid of m-n relations entirely and query for such relations manually. Which would be a shame of course.

Hey Dmitri 👋 thanks a lot for raising this, I’ve forwarded this to our Engineering team and will get back to as soon as possible with more information 🙂

Thanks @nikolasburk! Basically here’s a better explanation why one-way embedding is sometimes preferred https://learnmongodbthehardway.com/schema/schemabasics/#one-way-embedding

The reason we choose to embed all the references to categories in the books is due to there being lot more books in the drama category than categories in a book. If one embeds the books in the category document it’s easy to foresee that one could break the 16MB max document size for certain broad categories.

Ah thanks for the additional reference! I just checked with out Engineers and we definitely want to add more “patterns” for m:n relations in MongoDB in the future. We just started with the “Two Way Embedding” strategy since it seemed to be the most ubiquitous… It would however be super nice if you could create a GitHub issue for this and explain why the “One Way Embedding” can be more preferable at times.

I will! Absolutely! Prisma team rocks!

There should already be one for that...

@janpio the issues have a bit weird title. In my case I need a two-way relation, just modelled on a single end in Mongo (aka “One Way Embedding”)

I agree, see my edit history of the title on https://github.com/prisma/prisma/issues/12725 already 😄

“Support one-way embedding for Mongo m-n relations”?

Yeah that is how you and me would describe it - for others that does not make sense as they do not know the "one-way embedding" terminology 😄

@janpio well, this comment of yours sums it up pretty well https://github.com/prisma/prisma/issues/12552#issuecomment-1092126073

Yeah. I meant the first one - 12725 😄

ah. right. left a comment here https://github.com/prisma/prisma/issues/12725#issuecomment-1175264009

And I updated the title to use the more clear term.