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⚡ Bolt: Use Set for O(1) session lookups in schedule filter #236

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⚡ Bolt: Use Set for O(1) session lookups in schedule filter #236

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perf: use Set for O(1) session lookups in schedule filter
anyulled May 23, 2026
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perf: use Set for O(1) session lookups in schedule filter
anyulled May 23, 2026
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5 changes: 5 additions & 0 deletions .jules/bolt.md
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Expand Up @@ -2,3 +2,8 @@

**Learning:** In Next.js/React applications, when grouping items (like schedules or talks) into a `Map` where the values are arrays, using the array spread operator `[...existing, item]` inside a loop (like `forEach` or `map`) causes amortized O(N^2) memory allocations and unnecessary Garbage Collection overhead.
**Action:** Always use `.push()` on the existing array reference if the data structure permits local mutation. For strict ESLint configurations enforcing `no-restricted-syntax`, extract the existing array, push to it, and handle the fallback elegantly (`if (!existing) { map.set(key, [item]); } else { existing.push(item); }`).

## 2024-05-23 — O(1) Lookups inside filter loops

**Learning:** `Array.prototype.includes` within `Array.prototype.filter` or `.map` can create O(N*M) bottlenecks if the lookup array is sizable, negatively affecting JS execution time (especially on critical render paths for large lists like schedules).
**Action:** Always convert lookup arrays to `Set`s before array iteration and use `.has()` for O(1) checks. Ensure to place the `Set` initialization *outside\* any loops. Also, be sure to clean up `.orig` files created by patch tools before committing.
3 changes: 2 additions & 1 deletion components/schedule/ScheduleContainer.tsx
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Expand Up @@ -20,7 +20,8 @@ export default function ScheduleContainer({ initialSchedule, year }: Readonly<Sc
return initialSchedule;
}

const filterSessions = (sessions: GridSession[]) => sessions.filter((s) => savedSessionIds.includes(s.id) || s.isServiceSession);
const savedSessionIdsSet = new Set(savedSessionIds);
const filterSessions = (sessions: GridSession[]) => sessions.filter((s) => savedSessionIdsSet.has(s.id) || s.isServiceSession);
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@gemini-code-assist gemini-code-assist Bot May 23, 2026

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medium

While the current optimization to O(N+M) is excellent, you can further improve React performance by ensuring referential equality for rooms and sessions that are not affected by the filter. This prevents unnecessary re-renders of child components like SessionCard or ScheduleGrid sub-sections.

Consider checking if the filtered array length matches the original length to return the original reference.

    const savedSessionIdsSet = new Set(savedSessionIds);
    const filterSessions = (sessions: GridSession[]) => {
      const filtered = sessions.filter((s) => savedSessionIdsSet.has(s.id) || s.isServiceSession);
      return filtered.length === sessions.length ? sessions : filtered;
    };


return initialSchedule.map((day) => ({
...day,
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