From fc73f127ebeda4a2cff94564366cbf3e6ac5b2dc Mon Sep 17 00:00:00 2001
From: Adam Olley <adam.olley@blackboard.com>
Date: Mon, 6 Mar 2017 11:59:19 +1030
Subject: [PATCH] MDL-58160 coursecat: Use set_many to populate category cache

When the course category cache needs to be repopulated, two entries are added
to the cache for each category. In core this is currently done in a for-loop,
resulting in N set calls to the cache (where N is twice the number of
categories in Moodle).

This change switches that code to using a single set_many cache call instead,
which makes this an O(1) operation instead of O(N).

For a site with say, 1000 categories, this results in only 1 set call to the
cachestore instead of 2000.
---
 lib/coursecatlib.php | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/lib/coursecatlib.php b/lib/coursecatlib.php
index d8ce7b8cfa9..e5edde1a17b 100644
--- a/lib/coursecatlib.php
+++ b/lib/coursecatlib.php
@@ -626,9 +626,7 @@ class coursecat implements renderable, cacheable_object, IteratorAggregate {
         }
         // We must add countall to all in case it was the requested ID.
         $all['countall'] = $count;
-        foreach ($all as $key => $children) {
-            $coursecattreecache->set($key, $children);
-        }
+        $coursecattreecache->set_many($all);
         if (array_key_exists($id, $all)) {
             return $all[$id];
         }