optimize-loader

# Optimize Loader ## Anti-patterns to catch ### 1. Re-fetching data the caller already has If a loader fetches a record (e.g. `getVideoWithClipsById`) and then passes just the **ID** to a downstream function that re-fetches the same record internally — change the downstream function's signature to accept the already-fetched object. ```typescript // BAD — getNextVideoId internally calls getVideoWithClipsById again const video = yield * db.getVideoWithClipsById(videoId); const nextId = yield * db.getNextVideoId(videoId); // GOOD — pass the already-fetched video const video = yield * db.getVideoWithClipsById(videoId); const nextId = yield * db.getNextVideoId(video); ``` When refactoring signatures, type the parameter as the minimal shape needed, not the full return type: ```typescript // Accept only what the function actually reads function* (currentVideo: { id: string; lesson: { id: string; videos: Array<{ id: string; path: string }>; section: { repoVersion: { repo: { id: string } } }; } | null; }) ``` ### 2. Over-fetching nested relations If a function only needs IDs and paths for navigation but loads full nested trees including clips, transcripts, etc. — create a slim query variant. ```typescript // BAD — loads clips, chapters, thumbnails etc. just to get video IDs const course = yield * getCourseWithSectionsById(repoId); // GOOD — dedicated lightweight query const course = yield * getCourseNavigationData(repoId); ``` Slim query checklist: - `columns: { id: true, path: true }` — only select needed columns on leaf relations - `limit: 1` on relations like versions where you only need the latest - Omit `with:` for relations you don't traverse (clips, chapters, thumbnails) - Keep `where:` filters (e.g. `archived = false`) and `orderBy` intact ### 3. Sequential independent queries If a loader runs multiple independent DB calls sequentially, parallelize with `Effect.all`: ```typescript // BAD — sequential, total time = sum of both const nextVideoId = yield * db.getNextVideoId(video); const previousVideoId = yield * db.getPreviousVideoId(video); // GOOD — parallel, total time = max of both const [nextVideoId, previousVideoId] = yield * Effect.all([db.getNextVideoId(video), db.getPreviousVideoId(video)]); ``` ## Dependency injection pattern When adding a new query (like `getCourseNavigationData`) that lives in course operations but is used by video operations: 1. Add the query to `db-course-operations.server.ts` and export it 2. Declare the cross-domain dependency in `VideoOperationsService`'s `effect` block via `yield* CourseOperationsService` 3. The Effect Layer system resolves cross-domain dependencies automatically