From 58edaf607743861404639564bb32c9f6d50d469c Mon Sep 17 00:00:00 2001
From: Dirk Doesburg <dirk.doesburg@gmail.com>
Date: Wed, 10 Apr 2024 19:43:22 +0200
Subject: [PATCH] Optimize fetch_thumbnails (#3624)

In case of a redis backend, this should prevent doing a redis pipeline that looks for a thumbnail
for image "" many times, for each empty image field (such as a member without profile picture).

Consider for example this (partial) redis pipeline call from sentry:

```
"HGETALL 'djthumbs:thumbnails:avatars/98a3dd0519bae43a2bfc45f2bb8653a0.jpg'",
"HGETALL 'djthumbs:thumbnails:'",
"HGETALL 'djthumbs:thumbnails:'",
"HGETALL 'djthumbs:thumbnails:avatars/1152ba8439c354c207967279fcbf4fcb.jpg'",
"HGETALL 'djthumbs:thumbnails:'",
// ... (45 more)
```
---
 website/utils/media/services.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/website/utils/media/services.py b/website/utils/media/services.py
index 90402b2bd..c9f2cae92 100644
--- a/website/utils/media/services.py
+++ b/website/utils/media/services.py
@@ -89,6 +89,9 @@ def fetch_thumbnails(images: list, sizes=None):
     :param sizes: A list of sizes to prefetch. If None, all sizes will be prefetched.
     :return: None
     """
+    # Filter out empty ImageFieldFiles.
+    images = list(filter(bool, images))
+
     if not images:
         return