Drizzle Team•2y ago

Infer type for relational query

Is there anyway to infer the type of a relational queries result? For example if I have a user who makes posts which has comments. I have a relational query which gets me all my users, their posts and their comments nested. Is there a way to infer that type? Currently constructing the type myself from the tables in the schema.

7 Replies

mcgrealife•2y ago

@Dbeg I have achieved this by moving the query inside of a function, then using typescript's ReturnType helper.

const getUserWithPostsAndComments = async () => {
  const connection = connect({...})
  const db = drizzle(connection, { schema })

return db.query.users.findFirst({...})
}

export type CustomRelationType = ReturnType<typeof getUserWithPostsAndComments>

const getUserWithPostsAndComments = async () => {
  const connection = connect({...})
  const db = drizzle(connection, { schema })

return db.query.users.findFirst({...})
}

export type CustomRelationType = ReturnType<typeof getUserWithPostsAndComments>

I am using this pattern in nextjs api routes

DbegOP•2y ago

Oh ok yes that works! Thanks 😊 You probably were doing this but for anyone else, the return type of the async func would be a union type of the type | undefined wrapped in a promise. So this is what I did to get the exact type:

export type CustomRelationType = NonNullable<
  Awaited<ReturnType<typeof getUserWithPostsAndComments>>
>;

export type CustomRelationType = NonNullable<
  Awaited<ReturnType<typeof getUserWithPostsAndComments>>
>;

@mcgrealife Is this what you also had to do? or did I just do some longer for no reason. 🤣

mcgrealife•2y ago

Ah yes, I should have mentioned this too! Your Awaited implementation is actually cleaner than mine!, but same idea to unwrap the promise, yes! I have been using NonNullable anytime I use the type – it is much better to use it directly in the custom type definition! Thanks for the tip @Dbeg 👍

Cayter•2y ago

u guys did it wrongly let's say i'm using postgres driver

import * as schema from "./schema"; // your schema might be different path

const queryClient = postgres("postgres://postgres:[email protected]:5432/db");
const db: PostgresJsDatabase<typeof schema> = drizzle(queryClient);

import * as schema from "./schema"; // your schema might be different path

const queryClient = postgres("postgres://postgres:[email protected]:5432/db");
const db: PostgresJsDatabase<typeof schema> = drizzle(queryClient);

once you have defined your schema and the relations in the schema, the type inference will work the key point here is to ensure you declare your drizzle instance with typeof schema as the generic type well, by right the inference should work automatically without the above, i'm not sure if it's because of we split up the schema into different files

mcgrealife•2y ago

Ah I see. I answered a different question. Confirmed that my relation queries definitely infer their own return types (without manual type annotation)! I answered from the context of nextjs api files. Where the export type keyword can only be used in the outer scope. So I wrap the db query in a function defined in the outer scope, invoke that function from the inner scope, but export it's return type in the outer scope. Thanks Cayter

DbegOP•2y ago

Thanks @Cayter So I do have that and I realise I poorly worded my question. I actually was wondering if there was something along the lines of drizzle infer type from a schema method but for relations querties. so say I have a post table I can do something like this

export type Post = InferModel<typeof post>;

export type Post = InferModel<typeof post>;

I now have the exact type for Post that I can use, in say props for a component. Is there a way I could get a type for what is inferred? @mcgrealife method actually worked as well where i just take the inferred return type. Did not see anything in the docs about it get an explicit type for what a relation query could return.

Dan•2y ago

FWIW, a dedicated type for inferring model with relations is to be done - https://github.com/drizzle-team/drizzle-orm/issues/695

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Infer type for relational query