MBS-4967: Adding check for index_exists to upgrade.php

db/upgrade.php

@@ -528,7 +528,9 @@ function hvp_upgrade_2020091500() {
     $dbman = $DB->get_manager();
     $table = new xmldb_table('hvp_xapi_results');
     $index = new xmldb_index('results', XMLDB_INDEX_NOTUNIQUE, ['content_id', 'user_id']);
+    if (!$dbman->index_exists($table, $index)) {
         $dbman->add_index($table, $index);
+    }
 
     $oldindex = new xmldb_index('result', XMLDB_INDEX_UNIQUE, ['id', 'content_id', 'user_id']);
     $dbman->drop_index($table, $oldindex);