add index for models

submission/migrations/0004_submission_problem_user_idx.py

@@ -0,0 +1,19 @@
+# Generated by Django 6.0 on 2026-04-23 20:07
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('contest', '0003_acmcontestrank_acm_rank_contest_user_idx_and_more'),
+        ('problem', '0007_problem_problem_visible_idx'),
+        ('submission', '0003_add_contest_create_time_idx'),
+    ]
+
+    operations = [
+        migrations.AddIndex(
+            model_name='submission',
+            index=models.Index(fields=['problem_id', 'user_id'], name='problem_user_idx'),
+        ),
+    ]

submission/models.py

@@ -64,6 +64,9 @@ class Submission(models.Model):
             models.Index(
                 fields=["contest_id", "-create_time"], name="contest_create_time_idx"
             ),
+            models.Index(
+                fields=["problem_id", "user_id"], name="problem_user_idx"
+            ),
         ]
 
     def __str__(self):