Bug#35398028 : crash when persisted GR variable exist and

               GR plugin isn't loaded (during upgrade)

Description:
Server crashes on start up if the group replication plugin is
disabled or uninstalled after upgrade from version 8.0.28 in which
group replication variables were persisted.

Server does not load certain persisted group replication variables
when the plugin is installed after server start up.

Fix:
Handled the case of nullptr return value.

Added functionality to load parse early variables during plugin installation.

Change-Id: I04a96c8435f77e187648b7e5a9cc88cecaacd4f0

Author: Omar Sharieff

sql/persisted_variable.cc

@@ -897,6 +897,9 @@ void Persisted_variables_cache::set_parse_early_sources() {
 
   for (auto &it : sorted_vars) {
     auto sysvar = intern_find_sys_var(it.key.c_str(), it.key.length());
+    if (sysvar == nullptr) {
+      continue;
+    }
     sysvar->set_source(enum_variable_source::PERSISTED);
 #ifndef NDEBUG
     bool source_truncated =
@@ -1961,8 +1964,8 @@ int Persisted_variables_cache::read_persist_file() {
 
 /**
   append_parse_early_variables() does a lookup into persist_variables
-  for read only variables and place them after the command line options with a
-  separator "----persist-args-separator----"
+  for parse early variables and place them after the command line options with
+  a separator "----persist-args-separator----"
 
   This function does nothing when --no-defaults is set or if
   persisted_globals_load is disabled.

sql/sql_plugin.cc

@@ -2337,11 +2337,15 @@ static bool mysql_install_plugin(THD *thd, LEX_CSTRING name,
     }
     my_getopt_use_args_separator = false;
     /*
-     Append static variables present in mysqld-auto.cnf file for the
-     newly installed plugin to process those options which are specific
+     Append parse early and static variables present in mysqld-auto.cnf file
+     for the newly installed plugin to process those options which are specific
      to this plugin.
     */
-    if (pv && pv->append_read_only_variables(&argc, &argv, false, true)) {
+    bool arg_separator_added = false;
+    if (pv &&
+        (pv->append_parse_early_variables(&argc, &argv, arg_separator_added) ||
+         pv->append_read_only_variables(&argc, &argv, arg_separator_added,
+                                        true))) {
       mysql_mutex_unlock(&LOCK_plugin);
       mysql_rwlock_unlock(&LOCK_system_variables_hash);
       report_error(REPORT_TO_USER, ER_PLUGIN_IS_NOT_LOADED, name.str);