From 03ae00ae34ebde88fc3da7c7c3d3c7c5826ec615 Mon Sep 17 00:00:00 2001
From: henribru <6639509+henribru@users.noreply.github.com>
Date: Fri, 15 May 2020 16:08:22 +0200
Subject: [PATCH] Increase admin list panel performance by selecting related
 (#134)

* Increase admin panel performance by selecting related

* Use `get_changelist_instance` override
---
 easyaudit/admin.py         | 21 ++++++++++++++-------
 easyaudit/admin_helpers.py |  7 ++++++-
 2 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/easyaudit/admin.py b/easyaudit/admin.py
index 1e582a4a..b4de9661 100644
--- a/easyaudit/admin.py
+++ b/easyaudit/admin.py
@@ -26,13 +26,19 @@ class CRUDEventAdmin(EasyAuditModelAdmin):
                        'user_pk_as_string', 'datetime', 'changed_fields_prettified']
     exclude = ['object_json_repr', 'changed_fields']
 
+    def get_changelist_instance(self, *args, **kwargs):
+        changelist_instance = super().get_changelist_instance(*args, **kwargs)
+        content_type_ids = [obj.content_type_id for obj in changelist_instance.result_list]
+        self.content_types_by_id = {content_type.id: content_type for content_type in ContentType.objects.filter(id__in=content_type_ids)}
+        return changelist_instance
+
     def get_content_type(self, obj):
-        return ContentType.objects.get(id=obj.content_type_id)
+        return self.content_types_by_id[obj.content_type_id]
 
     get_content_type.short_description = "Content Type"
 
     def get_user(self, obj):
-        return get_user_model().objects.filter(id=obj.user_id).first()
+        return self.users_by_id.get(obj.user_id)
 
     get_user.short_description = "User"
 
@@ -41,9 +47,10 @@ def object_repr_link(self, obj):
             html = obj.object_repr
         else:
             try:
+                content_type = self.get_content_type(obj)
                 url = reverse("admin:%s_%s_change" % (
-                    obj.content_type.app_label,
-                    obj.content_type.model,
+                    content_type.app_label,
+                    content_type.model,
                 ), args=(obj.object_id,))
                 html = '<a href="%s">%s</a>' % (url, obj.object_repr)
             except:
@@ -76,12 +83,12 @@ class LoginEventAdmin(EasyAuditModelAdmin):
     readonly_fields = ['login_type', 'get_username', 'get_user', 'remote_ip', 'datetime', ]
 
     def get_user(self, obj):
-        return get_user_model().objects.filter(id=obj.user_id).first()
+        return self.users_by_id.get(obj.user_id)
 
     get_user.short_description = "User"
 
     def get_username(self, obj):
-        user = get_user_model().objects.filter(id=obj.user_id).first()
+        user = self.get_user(obj)
         username = user.get_username() if user else None
         return username
 
@@ -101,7 +108,7 @@ class RequestEventAdmin(EasyAuditModelAdmin):
     readonly_fields = ['url', 'method', 'query_string', 'get_user', 'remote_ip', 'datetime', ]
 
     def get_user(self, obj):
-        return get_user_model().objects.filter(id=obj.user_id).first()
+        return self.users_by_id.get(obj.user_id)
 
     get_user.short_description = "User"
 
diff --git a/easyaudit/admin_helpers.py b/easyaudit/admin_helpers.py
index 52a50c6e..11ae9b82 100644
--- a/easyaudit/admin_helpers.py
+++ b/easyaudit/admin_helpers.py
@@ -30,9 +30,14 @@ def prettify_json(json_string):
 
 
 class EasyAuditModelAdmin(admin.ModelAdmin):
+    def get_changelist_instance(self, *args, **kwargs):
+        changelist_instance = super().get_changelist_instance(*args, **kwargs)
+        user_ids = [obj.user_id for obj in changelist_instance.result_list]
+        self.users_by_id = {user.id: user for user in get_user_model().objects.filter(id__in=user_ids)}
+        return changelist_instance
 
     def user_link(self, obj):
-        user = get_user_model().objects.filter(id=obj.user_id).first()
+        user = self.users_by_id.get(obj.user_id)
         #return mark_safe(get_user_link(user))
         if user is None:
             return '-'