Request batching - single db query

[mmkal]

In the docs about request batching it says that the post by id queries will result in one request and one database query. The one request part I understand, but doesn't the one database query assertion depend on whether the server uses a dataloader, or something similar?

[KATT]

Hey!

Yeah, your backend needs to have a dataloader or similar.

If you use Prisma, you get this behaviour out-of-the-box as their .findUnique()-etc waits a tick before being called. How that works you can see in their video here: https://www.youtube.com/watch?v=7oMfBGEdwsc

For a reference example, you can pull down the next-prisma-starter and comment out these lines

trpc/examples/next-prisma-starter/src/pages/index.tsx

Lines 12 to 16 in d2e8839

	// useEffect(() => {
	// postsQuery.data?.forEach((post) => {
	// utils.prefetchQuery(['post.byId', post.id]);
	// });
	// }, [postsQuery.data, utils]);

The above will prefetch all the data from the post.byId-procedures as 1 single batch HTTP call and since they are using findUnique() they will actually be all called the same DB query.

If you run the project in development mode you all the queries made are logged so you can see it for yourself :)

[mmkal]

Got it. Thanks - we don't use prisma so was curious what magic trpc would do here. IMO it's a prisma feature that fits nicely with trpc here, but maybe worth calling out so people don't think trpc will do any low-level magic.

[KATT]

Agreed. Feel free to make a amendment if you want :)