Fix duplicate partners in paginated list and API

apps/web/lib/api/pagination.ts

@@ -78,8 +78,6 @@ export function buildPaginationQuery(filters: Filters): PaginationQuery {
   }
 
   return {
-    // Order by id only for better query performance on large datasets (single-column PK index).
-    // Trade-off: ordering is by id rather than createdAt, so order may not strictly match creation time.
     orderBy: {
       [sortBy]: sortOrder,
     },

apps/web/lib/api/partners/get-partners.ts

@@ -56,9 +56,7 @@ export async function getPartners(filters: PartnerFilters) {
     },
     take: pageSize,
     skip: (page - 1) * pageSize,
-    orderBy: {
-      [sortBy]: sortOrder,
-    },
+    orderBy: [{ [sortBy]: sortOrder }, { id: sortOrder }],
   });
 
   return partners.map(

apps/web/tests/partners/pagination.test.ts

@@ -0,0 +1,65 @@
+import { EnrolledPartnerProps } from "@/lib/types";
+import { beforeAll, describe, expect, test } from "vitest";
+import { expectNoOverlap } from "../utils/helpers";
+import { IntegrationHarness } from "../utils/integration";
+
+describe.concurrent("/partners/** - pagination", async () => {
+  const h = new IntegrationHarness();
+  let http: IntegrationHarness["http"];
+  let baseline: EnrolledPartnerProps[];
+  let baselineIds: string[];
+
+  const commonQuery = {
+    pageSize: "5",
+    sortBy: "totalSaleAmount",
+    sortOrder: "desc",
+  };
+
+  beforeAll(async () => {
+    ({ http } = await h.init());
+
+    const { status, data } = await http.get<EnrolledPartnerProps[]>({
+      path: "/partners",
+      query: { ...commonQuery, pageSize: "100" },
+    });
+
+    expect(status).toEqual(200);
+
+    baseline = data;
+    baselineIds = baseline.map((p) => p.id);
+    expect(baselineIds.length).toBeGreaterThanOrEqual(15);
+  });
+
+  test("Offset pagination has no duplicate partners across pages", async () => {
+    const page1 = await http.get<EnrolledPartnerProps[]>({
+      path: "/partners",
+      query: { ...commonQuery, page: "1" },
+    });
+    const page2 = await http.get<EnrolledPartnerProps[]>({
+      path: "/partners",
+      query: { ...commonQuery, page: "2" },
+    });
+    const page3 = await http.get<EnrolledPartnerProps[]>({
+      path: "/partners",
+      query: { ...commonQuery, page: "3" },
+    });
+
+    expect(page1.status).toEqual(200);
+    expect(page2.status).toEqual(200);
+    expect(page3.status).toEqual(200);
+    expect(page1.data).toHaveLength(5);
+    expect(page2.data).toHaveLength(5);
+    expect(page3.data).toHaveLength(5);
+
+    expectNoOverlap(page1.data, page2.data);
+    expectNoOverlap(page2.data, page3.data);
+    expectNoOverlap(page1.data, page3.data);
+
+    const paginatedIds = [...page1.data, ...page2.data, ...page3.data].map(
+      (p) => p.id,
+    );
+
+    expect(new Set(paginatedIds).size).toBe(paginatedIds.length);
+    expect(paginatedIds).toEqual(baselineIds.slice(0, paginatedIds.length));
+  });
+});