From d9273a64e984ec46759b85d8e55ed66cc72e8249 Mon Sep 17 00:00:00 2001
From: Ferdinand Thiessen <opensource@fthiessen.de>
Date: Tue, 14 Jul 2026 21:05:10 +0200
Subject: [PATCH] fix(redis): properly clear keys from cluster

Signed-off-by: Ferdinand Thiessen <opensource@fthiessen.de>
---
 lib/private/Memcache/Redis.php | 31 ++++++++++++++++++++++---------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/lib/private/Memcache/Redis.php b/lib/private/Memcache/Redis.php
index 9c8eb4aaee979..2ebe7a2634866 100644
--- a/lib/private/Memcache/Redis.php
+++ b/lib/private/Memcache/Redis.php
@@ -100,16 +100,29 @@ public function remove($key): bool {
 
 	#[\Override]
 	public function clear($prefix = '') {
-		// TODO: this is slow and would fail with Redis cluster
-		$prefix = $this->getPrefix() . $prefix . '*';
-		/** @var list<string>|false -- we are not in MULTI mode, so we can cast the return value here */
-		$keys = $this->getCache()->keys($prefix);
-		if ($keys === false) {
-			return false;
+		$pattern = $this->getPrefix() . $prefix . '*';
+		$deletedTotal = 0;
+		$expectedTotal = 0;
+		$iterator = null;
+		while (true) {
+			$keys = $this->getCache()->scan($iterator, $pattern, 1000);
+			if ($keys === false) {
+				break;
+			}
+
+			if (!empty($keys)) {
+				$expectedTotal += count($keys);
+				$result = $this->getCache()->del($keys);
+				if (is_int($result)) {
+					$deletedTotal += $result;
+				}
+			}
+
+			if ($iterator === 0) {
+				break;
+			}
 		}
-
-		$deleted = $this->getCache()->del($keys);
-		return count($keys) === $deleted;
+		return $deletedTotal === $expectedTotal;
 	}
 
 	#[\Override]