fix(analytics): use COUNT(DISTINCT viewer_id) for uniqueViewers instead of groupBy composite key (#449)

Author: Srejoye

apps/backend/src/routes/analytics.ts

@@ -70,13 +70,14 @@ export async function analyticsRoutes(
       // Count unique viewers
       // In raw SQL this is `SELECT COUNT(DISTINCT viewer_id) FROM card_views WHERE owner_id = ?`
       // Prisma group-by as workaround:
-      const uniqueViewersQuery =
-        await app.prisma.cardView.groupBy({
-          by: ['viewerId', 'viewerIp'],
-          where: { ownerId: userId },
-        });
-
-      const uniqueViewers = uniqueViewersQuery.length;
+      const uniqueViewersQuery = await app.prisma.$queryRaw<[{ count: bigint }]>`
+        SELECT COUNT(DISTINCT viewer_id) AS count
+        FROM card_views
+        WHERE owner_id = ${userId}
+        AND viewer_id IS NOT NULL
+      `;
+
+      const uniqueViewers = Number(uniqueViewersQuery[0]?.count ?? 0);
 
       return {
         totalViews,