diff --git a/packages/hydrooj/package.json b/packages/hydrooj/package.json
index 493728179..9cabad2b9 100644
--- a/packages/hydrooj/package.json
+++ b/packages/hydrooj/package.json
@@ -1,6 +1,6 @@
 {
     "name": "hydrooj",
-    "version": "2.17.14",
+    "version": "2.17.15",
     "bin": "bin/hydrooj.js",
     "main": "dist/loader.js",
     "typings": "dist/loader.d.ts",
diff --git a/packages/hydrooj/src/upgrade.ts b/packages/hydrooj/src/upgrade.ts
index 01e2c246e..2683d3f03 100644
--- a/packages/hydrooj/src/upgrade.ts
+++ b/packages/hydrooj/src/upgrade.ts
@@ -27,8 +27,14 @@ async function iterateAllDomain(cb: (ddoc: DomainDoc, current?: number, total?:
 
 async function iterateAllProblem(fields: problem.Pdoc.Field[], cb: (pdoc: problem.Pdoc, current?: number, total?: number) => Promise<any>) {
     await iterateAllDomain(async (d) => {
-        const pdocs = await problem.getMulti(d._id, {}, fields).toArray();
-        for (const i in pdocs) await cb(pdocs[i], +i, pdocs.length);
+        const cursor = problem.getMulti(d._id, {}, fields);
+        const total = await problem.getMulti(d._id, {}).count();
+        let i = 0;
+        while (await cursor.hasNext()) {
+            const doc = await cursor.next();
+            i++;
+            await cb(doc, i, total);
+        }
     });
 }
 
@@ -154,6 +160,24 @@ const scripts: UpgradeScript[] = [
         });
         return true;
     },
+    async function _8_9() {
+        const _FRESH_INSTALL_IGNORE = 1;
+        await iterateAllProblem(['docId', 'domainId'], async (pdoc) => {
+            logger.info('%s/%s', pdoc.domainId, pdoc.docId);
+            const [data, additional_file] = await Promise.all([
+                storage.list(`problem/${pdoc.domainId}/${pdoc.docId}/testdata/`),
+                storage.list(`problem/${pdoc.domainId}/${pdoc.docId}/additional_files/`),
+            ]) as any;
+            for (let i = 0; i < data.length; i++) {
+                data[i]._id = data[i].name;
+            }
+            for (let i = 0; i < additional_file.length; i++) {
+                additional_file[i]._id = additional_file[i].name;
+            }
+            await problem.edit(pdoc.domainId, pdoc.docId, { data, additional_file });
+        });
+        return true;
+    },
 ];
 
 export = scripts;