diff --git a/my/lib.php b/my/lib.php
index 8ad1e7029db..3192c3293f4 100644
--- a/my/lib.php
+++ b/my/lib.php
@@ -149,29 +149,18 @@ function my_reset_page_for_all_users($private = MY_PAGE_PRIVATE, $pagetype = 'my
     // This may take a while. Raise the execution time limit.
     core_php_time_limit::raise();
 
-    // Find all the user pages.
-    $where = 'userid IS NOT NULL AND private = :private';
-    $params = array('private' => $private);
-    $pages = $DB->get_recordset_select('my_pages', $where, $params, 'id, userid');
-    $blockids = array();
-
-    foreach ($pages as $page) {
-        $usercontext = context_user::instance($page->userid);
-
-        // Find all block instances in that page.
-        $blockswhere = 'parentcontextid = :parentcontextid AND
-            pagetypepattern = :pagetypepattern AND
-            (subpagepattern IS NULL OR subpagepattern = :subpagepattern)';
-        $blockswhereparams = [
-            'parentcontextid' => $usercontext->id,
-            'pagetypepattern' => $pagetype,
-            'subpagepattern' => $page->id
-        ];
-        if ($pageblockids = $DB->get_fieldset_select('block_instances', 'id', $blockswhere, $blockswhereparams)) {
-            $blockids = array_merge($blockids, $pageblockids);
-        }
-    }
-    $pages->close();
+    // Find all the user pages and all block instances in them.
+    $sql = "SELECT bi.id
+        FROM {my_pages} p
+        JOIN {context} ctx ON ctx.instanceid = p.userid AND ctx.contextlevel = :usercontextlevel
+        JOIN {block_instances} bi ON bi.parentcontextid = ctx.id AND
+            bi.pagetypepattern = :pagetypepattern AND
+            (bi.subpagepattern IS NULL OR bi.subpagepattern = " . $DB->sql_concat("''", 'p.id') . ")
+        WHERE p.private = :private";
+    $params = array('private' => $private,
+        'usercontextlevel' => CONTEXT_USER,
+        'pagetypepattern' => $pagetype);
+    $blockids = $DB->get_fieldset_sql($sql, $params);
 
     // Wrap the SQL queries in a transaction.
     $transaction = $DB->start_delegated_transaction();
@@ -182,9 +171,7 @@ function my_reset_page_for_all_users($private = MY_PAGE_PRIVATE, $pagetype = 'my
     }
 
     // Finally delete the pages.
-    if (!empty($pages)) {
-        $DB->delete_records_select('my_pages', $where, $params);
-    }
+    $DB->delete_records_select('my_pages', 'userid IS NOT NULL AND private = :private', ['private' => $private]);
 
     // We should be good to go now.
     $transaction->allow_commit();