findByIds Deprecated about lireddit HOT 1 OPEN

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}`];
	})
})