findByIds Deprecated

[csandoval18]

I'm in minute 11:36:00 of the tutorial, and I noticed that findById was deprecated when implementing the createUserLoader function. I was able to get around it by doing the following:

export const createUserLoader = () =>
	new DataLoader<number, Users>(async (userIds) => {
		const users = await Users.findBy({ id: In(userIds as number[]) })
		const userIdToUser: Record<number, Users> = {}
		users.forEach((u) => {
			userIdToUser[u.id] = u
		})

		const sortedUsers = userIds.map((userId) => userIdToUser[userId])
		return sortedUsers
	})

As you can see I used findBy instead of findByIds and the In function provided by typeorm. I tried using the same approach for the createUpdootLoader, but I noticed that it did not work since I needed to search for both the userId and the postId to retrieve the corresponding upvotes. Was anyone able to implement that correctly? I am unsure how to use findBy to search multiple fields with the keys since I cannot seem to separate the key fields by using keys.userId and keys.postId. This is my current code:

export const createUpdootLoader = () =>
	new DataLoader<{ postId: number; userId: number }, Updoot | null>(
		async (keys) => {
			console.log('keys:', keys)
			const updoots = await Updoot.findby({userId:  In(keys as any} )
			const updootIdsToUpdoot: Record<string, Upvotes> = {}
			updoots.forEach((updoot) => {
				upvoteIdsToUpvote[`${updoot.userId} | ${updoot.postId}`] = updoot
			})

			const sortedUpdoot = keys.map(
				(key) => updootIdsToUpdoot[`${key.userId} | ${key.postId}`],
			)
			return sortedUpdoots
		},

[adeniyii]

Hey @csandoval18 , here's how I was able to solve it, though I'm not 100% sure it's the right approach.

Basically, I map over the list of key-value objects to extract the userIds and postIds into separate arrays. Then apply them as separate search criteria in the findBy function. After that, I generate an updootToIdMap with the key as a string of format: <postId>|<userId> and the value as a returned updoot. Finally, I return the array of updoots in the same order the initial object array idObjArr was provided.

Hope this helps!

import DataLoader from "dataloader";
import { In } from "typeorm";
import { Updoot } from "../entities/Updoot";

// A data loader takes a list of keys (in this instance, a list of objects of keys),
// and returns a list of corresponding entities - updoots | null in the same order as the given keys.
// Data loaders batch and cache database requests to avoid the N + 1 problem of
// fetching N requests for a single db query
export const createUpdootLoader = () => new DataLoader<{userId: number, postId: number}, Updoot | null>(async (idObjArr) => {
	const userIds = idObjArr.map(obj => obj.userId)
	const postIds = idObjArr.map(obj => obj.postId)
	const updoots = await Updoot.findBy({userId: In(userIds), postId: In(postIds)})

	const updootToIdMap: Record<string, Updoot> = {}
	updoots.forEach(updoot => {
		updootToIdMap[`${updoot.postId}|${updoot.userId}`] = updoot
	})

	return idObjArr.map(obj => {
		return updootToIdMap[`${obj.postId}|${obj.userId}`];
	})
})

This is the SQL that was generated when the loader is executed.