From 641ce4237ef3fec6752f097a695d81d2949e6920 Mon Sep 17 00:00:00 2001
From: Zoe Roux <zoe.roux@zoriya.dev>
Date: Tue, 7 Jan 2025 16:28:37 +0100
Subject: [PATCH] Use an array as a backing store for after

---
 api/src/models/utils/keyset-paginate.ts | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/api/src/models/utils/keyset-paginate.ts b/api/src/models/utils/keyset-paginate.ts
index d6710af3..81610499 100644
--- a/api/src/models/utils/keyset-paginate.ts
+++ b/api/src/models/utils/keyset-paginate.ts
@@ -3,9 +3,7 @@ import { eq, or, type Column, and, gt, lt } from "drizzle-orm";
 
 type Table<Name extends string> = Record<Name, Column>;
 
-type After = Record<string, string | number | boolean | undefined> & {
-	reverse?: boolean;
-};
+type After = [boolean, ...[string | number | boolean | undefined]];
 
 // Create a filter (where) expression on the query to skip everything before/after the referenceID.
 // The generalized expression for this in pseudocode is:
@@ -31,18 +29,20 @@ export const keysetPaginate = <
 	sort: Sort<T, Remap>;
 }) => {
 	if (!after) return undefined;
-	const { reverse, ...cursor }: After = JSON.parse(
+	const [reverse, ...cursor]: After = JSON.parse(
 		Buffer.from(after, "base64").toString("utf-8"),
 	);
 
+	const pkSort = { key: "pk" as const, desc: false };
+
 	// TODO: Add an outer query >= for perf
 	// PERF: See https://use-the-index-luke.com/sql/partial-results/fetch-next-page#sb-equivalent-logic
 	let where = undefined;
 	let previous = undefined;
-	for (const by of [...sort, { key: "pk" as const, desc: false }]) {
+	for (const [i, by] of [...sort, pkSort].entries()) {
 		const cmp = by.desc !== reverse ? lt : gt;
-		where = or(where, and(previous, cmp(table[by.key], cursor[by.key])));
-		previous = and(previous, eq(table[by.key], cursor[by.key]));
+		where = or(where, and(previous, cmp(table[by.key], cursor[i])));
+		previous = and(previous, eq(table[by.key], cursor[i]));
 	}
 
 	return where;
@@ -53,9 +53,10 @@ export const generateAfter = (
 	sort: Sort<any, any>,
 	reverse?: boolean,
 ) => {
-	const ret: After = { reverse };
-	for (const by of sort) {
-		ret[by.key] = cursor[by.key];
-	}
+	const ret = [
+		reverse ?? false,
+		...sort.map((by) => cursor[by.key]),
+		cursor.pk,
+	];
 	return Buffer.from(JSON.stringify(ret), "utf-8").toString("base64");
 };