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52 lines
1.3 KiB
Markdown
52 lines
1.3 KiB
Markdown
---
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title: Dependency-Based Parallelization
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impact: CRITICAL
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impactDescription: 2-10× improvement
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tags: async, parallelization, dependencies, better-all
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---
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## Dependency-Based Parallelization
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For operations with partial dependencies, use `better-all` to maximize parallelism. It automatically starts each task at the earliest possible moment.
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**Incorrect (profile waits for config unnecessarily):**
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```typescript
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const [user, config] = await Promise.all([
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fetchUser(),
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fetchConfig()
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])
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const profile = await fetchProfile(user.id)
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```
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**Correct (config and profile run in parallel):**
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```typescript
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import { all } from 'better-all'
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const { user, config, profile } = await all({
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async user() { return fetchUser() },
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async config() { return fetchConfig() },
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async profile() {
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return fetchProfile((await this.$.user).id)
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}
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})
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```
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**Alternative without extra dependencies:**
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We can also create all the promises first, and do `Promise.all()` at the end.
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```typescript
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const userPromise = fetchUser()
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const profilePromise = userPromise.then(user => fetchProfile(user.id))
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const [user, config, profile] = await Promise.all([
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userPromise,
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fetchConfig(),
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profilePromise
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])
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```
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Reference: [https://github.com/shuding/better-all](https://github.com/shuding/better-all)
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