perf(webapp): avoid unindexed fileId scan in get-background-worker-by-version

The endpoint loaded each file's tasks via the files.tasks relation, which
queries BackgroundWorkerTask by the unindexed fileId column and
sequential-scans a very large table for every request.

Group task slugs by fileId in memory from the tasks that are already loaded
via the indexed workerId relation, and drop the files.tasks include. The
response shape is unchanged.

Author: d-cs

.server-changes/background-worker-version-endpoint-tasks.md

@@ -0,0 +1,6 @@
+---
+area: webapp
+type: improvement
+---
+
+Speed up retrieving a background worker by version. The endpoint no longer runs a slow lookup that scanned the full task table for large deployments; it now reuses data it already loads, so the response is the same but returns much faster.

apps/webapp/app/routes/api.v1.projects.$projectRef.background-workers.$envSlug.$version.ts

@@ -45,22 +45,27 @@ export async function loader({ params, request }: LoaderFunctionArgs) {
       },
       include: {
         tasks: true,
-        files: {
-          include: {
-            tasks: {
-              select: {
-                slug: true,
-              },
-            },
-          },
-        },
+        files: true,
       },
     });
 
     if (!backgroundWorker) {
       return json({ error: "Background worker not found" }, { status: 404 });
     }
 
+    // Group task slugs by fileId from the already-loaded tasks (which are fetched
+    // via the indexed workerId relation) instead of loading files.tasks, which
+    // queries BackgroundWorkerTask by the unindexed fileId column.
+    const taskSlugsByFileId = new Map<string, Set<string>>();
+    for (const task of backgroundWorker.tasks) {
+      if (!task.fileId) {
+        continue;
+      }
+      const slugs = taskSlugsByFileId.get(task.fileId) ?? new Set<string>();
+      slugs.add(task.slug);
+      taskSlugsByFileId.set(task.fileId, slugs);
+    }
+
     return json({
       id: backgroundWorker.friendlyId,
       version: backgroundWorker.version,
@@ -82,7 +87,7 @@ export async function loader({ params, request }: LoaderFunctionArgs) {
         filePath: file.filePath,
         contentHash: file.contentHash,
         contents: decompressContent(file.contents),
-        tasks: Array.from(new Set(file.tasks.map((task) => task.slug))),
+        tasks: Array.from(taskSlugsByFileId.get(file.id) ?? []),
       })),
     });
   } catch (error) {