perf(artists): memoise filter pipeline and list-view grouping (#250)

Artists.tsx already paginates the DOM via PAGE_SIZE + IntersectionObserver,
so the page never holds more than 50-100 cards at a time. The actual
overhead with a 5000-artist library was the filter pipeline running on
every render — including renders triggered by selection mode toggles,
view-mode switches, image-toggle, etc. — re-walking the full artists
array twice per render (letterFilter + search filter), then re-building
the list-view groups Record from scratch.

Wrap the pipeline in useMemo:

- `filtered` recomputes only when artists / letterFilter / filter change
- `visible` recomputes only when filtered / visibleCount change
  (also keeps array identity stable across unrelated re-renders)
- `groups` + `letters` recompute only when visible / viewMode change,
  and skip the loop entirely in grid view (where they're unused)

No new dependency. With 5000 artists, unrelated state changes
(selection toggle, click on a card, scroll past pagination boundary)
are noticeably smoother.

Confirmed locally on a ~5000-artist library.

Co-authored-by: Psychotoxical <dev@psysonic.app>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Frank Stellmacher
2026-04-21 21:38:11 +02:00
committed by GitHub
parent aa0776e811
commit 0dfc3fcfe2
+34 -26
View File
@@ -1,4 +1,4 @@
import React, { useEffect, useState, useCallback, useRef } from 'react';
import React, { useEffect, useState, useCallback, useRef, useMemo } from 'react';
import { useNavigate } from 'react-router-dom';
import { getArtists, SubsonicArtist, buildCoverArtUrl, coverArtCacheKey } from '../api/subsonic';
import { LayoutGrid, List, Images, CheckSquare2, ListMusic, Check } from 'lucide-react';
@@ -131,23 +131,27 @@ export default function Artists() {
setVisibleCount(PAGE_SIZE);
}, [filter, letterFilter, viewMode, PAGE_SIZE]);
// Filter pipeline
let filtered = artists;
// Filter pipeline — memoised so unrelated state changes (selection mode,
// viewMode, etc.) don't re-iterate the full artists array. With 5000+
// artists each re-render walked the list twice without this.
const filtered = useMemo(() => {
let out = artists;
if (letterFilter !== ALL_SENTINEL) {
out = out.filter(a => {
const first = a.name[0]?.toUpperCase() ?? '#';
const isAlpha = /^[A-Z]$/.test(first);
if (letterFilter === '#') return !isAlpha;
return first === letterFilter;
});
}
if (filter) {
const needle = filter.toLowerCase();
out = out.filter(a => a.name.toLowerCase().includes(needle));
}
return out;
}, [artists, letterFilter, filter]);
if (letterFilter !== ALL_SENTINEL) {
filtered = filtered.filter(a => {
const first = a.name[0]?.toUpperCase() ?? '#';
const isAlpha = /^[A-Z]$/.test(first);
if (letterFilter === '#') return !isAlpha;
return first === letterFilter;
});
}
if (filter) {
filtered = filtered.filter(a => a.name.toLowerCase().includes(filter.toLowerCase()));
}
const visible = filtered.slice(0, visibleCount);
const visible = useMemo(() => filtered.slice(0, visibleCount), [filtered, visibleCount]);
const hasMore = visibleCount < filtered.length;
// Intersection Observer for infinite scroll (after hasMore declaration)
@@ -160,15 +164,19 @@ export default function Artists() {
return () => observer.disconnect();
}, [loadMore, hasMore]);
// Group by first letter (for list view)
const groups: Record<string, SubsonicArtist[]> = {};
visible.forEach(a => {
const letter = a.name[0]?.toUpperCase() ?? '#';
const key = /^[A-Z]$/.test(letter) ? letter : '#';
if (!groups[key]) groups[key] = [];
groups[key].push(a);
});
const letters = Object.keys(groups).sort();
// Group by first letter (for list view) — only recompute when the visible
// slice or the view mode actually changes. Skipped entirely in grid view.
const { groups, letters } = useMemo(() => {
if (viewMode !== 'list') return { groups: {} as Record<string, SubsonicArtist[]>, letters: [] as string[] };
const g: Record<string, SubsonicArtist[]> = {};
for (const a of visible) {
const letter = a.name[0]?.toUpperCase() ?? '#';
const key = /^[A-Z]$/.test(letter) ? letter : '#';
if (!g[key]) g[key] = [];
g[key].push(a);
}
return { groups: g, letters: Object.keys(g).sort() };
}, [visible, viewMode]);
return (
<div className="content-body animate-fade-in">