chore: add allow_download field to existing Document records

--bug=1060848 --user=刘瑞斌 【知识库】文档设置[允许知识库来源中下载 ]应该默认开启 https://www.tapd.cn/62980211/s/1762365

apps/knowledge/migrations/0002_alter_file_source_type.py

@@ -1,24 +1,29 @@
 # Generated by Django 5.2.4 on 2025-08-11 09:45
 
-from django.db import migrations, models
+from django.db import migrations, models, connection
+
 
-from django.db.models import Q
 
 
 def add_allow_download_to_existing_documents(apps, schema_editor):
-    Document = apps.get_model('knowledge', 'Document')
 
-    # 为所有现有的Document记录添加allow_download=True
-    documents = Document.objects.filter(
-        Q(meta__isnull=True) |
-        ~Q(meta__has_key='allow_download')
-    )
+    # 使用原生SQL进行批量更新，避免加载大量对象到内存
+    with connection.cursor() as cursor:
+        # 为meta为null的记录设置初始值
+        cursor.execute("""
+                       UPDATE document
+                       SET meta = '{"allow_download": true}'::jsonb
+                       WHERE meta IS NULL
+                       """)
+
+        # 为meta不包含allow_download键的记录添加该字段
+        cursor.execute("""
+                       UPDATE document
+                       SET meta = meta || '{"allow_download": true}'::jsonb
+                       WHERE meta IS NOT NULL
+                         AND NOT (meta ? 'allow_download')
+                       """)
 
-    for doc in documents:
-        if doc.meta is None:
-            doc.meta = {}
-        doc.meta['allow_download'] = True
-        doc.save(update_fields=['meta'])
 
 class Migration(migrations.Migration):