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feat: [performance improvement] Parallelize data fetching in talks generateStaticParams #252

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feat: [performance improvement] Parallelize data fetching in talks ge…
anyulled Jun 1, 2026
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feat: [performance improvement] Parallelize data fetching in talks ge…
anyulled Jun 1, 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); }`).

## 2024-05-19 - Parallelize next build generateStaticParams

**Learning:** When `generateStaticParams` uses a sequential `for...of` loop to iterate over multiple parameters (like event years) and fetches external data, it forces Next.js to wait sequentially for each fetch to finish before starting the next. This creates a significant, O(N) performance bottleneck during the build step.
**Action:** Replace sequential `for...of` loops with `await Promise.all(items.map(async (item) => { ... }))`. By mapping each item into an async data-fetching promise, Next.js executes the requests concurrently, resulting in significantly faster build times. Always make sure to preserve per-item `try/catch` fallbacks to avoid failing the entire batch if a single item errors.
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@gemini-code-assist gemini-code-assist Bot Jun 1, 2026

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medium

The recommendation to 'always preserve per-item try/catch fallbacks to avoid failing the entire batch' contradicts the repository's general rule. For build-time data fetching, we want failures to halt the build so we do not deploy incomplete pages. Please update this documentation to recommend using strict mode for build-time data fetching.

References
  1. Data fetching functions used during the build process (e.g., for sitemap generation) should include a 'strict' mode that throws an error on failure. This ensures that data fetching problems cause the build to fail, preventing the deployment of incomplete pages.

26 changes: 13 additions & 13 deletions app/[year]/talks/[talkId]/page.tsx
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Expand Up @@ -29,21 +29,21 @@ interface TalkDetailProps {

export async function generateStaticParams() {
const years = getArchivedEditions();
const params = [];

for (const year of years) {
try {
const sessionGroups = await getTalks(year);
const allTalks = sessionGroups.flatMap((group) => group.sessions);
for (const talk of allTalks) {
params.push({ year, talkId: talk.id });

const nestedParams = await Promise.all(
years.map(async (year) => {
try {
const sessionGroups = await getTalks(year);
const allTalks = sessionGroups.flatMap((group) => group.sessions);
return allTalks.map((talk) => ({ year, talkId: talk.id }));
} catch (error) {
console.warn(`Failed to fetch talks for year ${year}:`, error);
return [];
}
} catch (error) {
console.warn(`Failed to fetch talks for year ${year}:`, error);
}
}
})
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@gemini-code-assist gemini-code-assist Bot Jun 1, 2026

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high

According to the repository's general rules, data fetching functions used during the build process (such as generateStaticParams) should run in strict mode. This ensures that any data fetching failure correctly halts the build, preventing the deployment of incomplete pages with missing talks. Swallowing the error and returning an empty array allows the build to succeed silently with incomplete data.

    years.map(async (year) => {
      const sessionGroups = await getTalks(year, { strict: true });
      const allTalks = sessionGroups.flatMap((group) => group.sessions);
      return allTalks.map((talk) => ({ year, talkId: talk.id }));
    })
References
  1. Data fetching functions used during the build process (e.g., for sitemap generation) should include a 'strict' mode that throws an error on failure. This ensures that data fetching problems cause the build to fail, preventing the deployment of incomplete pages.

);

return params;
return nestedParams.flat();
}

export async function generateMetadata({ params }: TalkDetailProps): Promise<Metadata> {
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