Updating a many-to-many relationship in Prisma - prisma

Question

I'm trying to figure out the right way to implement an upsert/update of the following schema:
model Post {
author String #Id
lastUpdated DateTime #default(now())
categories Category[]
}
model Category {
id Int #id
posts Post[]
}
Here is what I'd like to do. Get a post with category ids attached to it and insert it into the schema above.
The following command appears to insert the post
const post = await prisma.post.upsert({
where:{
author: 'TK'
},
update:{
lastUpdated: new Date()
},
create: {
author: 'TK'
}
})
My challenge is how do I also upsert the Category. I'll be getting a list of Catogories in the like 1,2,3 and if they do not exist I need to insert it into the category table and add the post to it. If the category does exist, I need to update the record with the post I inserted above preserving all attached posts.
Would appreciate it if I could be pointed in the right direction.

Answer 1

For the model, it can be simplified as follows as Prisma supports #updatedAt which will automatically update the column:
model Post {
author String #id
lastUpdated DateTime #updatedAt
categories Category[]
}
model Category {
id Int #id
posts Post[]
}
As for the query, it would look like this:
const categories = [
{ create: { id: 1 }, where: { id: 1 } },
{ create: { id: 2 }, where: { id: 2 } },
]
await db.post.upsert({
where: { author: 'author' },
create: {
author: 'author',
categories: {
connectOrCreate: categories,
},
},
update: {
categories: { connectOrCreate: categories },
},
})
connectOrCreate will create if not present and add the categories to the posts as well.