MDEV-39207 Fix plugin name passed to find_bookmark in test_plugin_options

Should be lowercase, just like in construct_options(). Without this
fix all plugin session vars have test_load always
false (static_unloaded).

Author: mariadb-YuchenPei

mysql-test/suite/sys_vars/r/session_track_system_variables_basic.result

@@ -152,3 +152,38 @@ SET SESSION session_track_system_variables="sql_slave_skip_counter", sql_slave_s
 # Restoring the original values.
 SET @@global.session_track_system_variables = @global_saved_tmp;
 # End of tests.
+#
+# MDEV-39207 plugin variables disappear from session_track_system_variables list
+#
+install soname 'ha_example.so';
+# Plugin global vars are not included
+set global session_track_system_variables='myisam_block_size';
+select @@global.session_track_system_variables;
+@@global.session_track_system_variables
+
+set global session_track_system_variables='example_int_var';
+select @@global.session_track_system_variables;
+@@global.session_track_system_variables
+example_int_var
+set global session_track_system_variables='myisam_sort_buffer_size,example_int_var';
+select @@global.session_track_system_variables;
+@@global.session_track_system_variables
+example_int_var,myisam_sort_buffer_size
+set global session_track_system_variables='myisam_block_size,myisam_sort_buffer_size,character_set_client,example_int_var';
+select @@global.session_track_system_variables;
+@@global.session_track_system_variables
+character_set_client,example_int_var,myisam_sort_buffer_size
+# Session tracking works as expected for plugin session var
+connect foo,localhost,root;
+select @@session.session_track_system_variables;
+@@session.session_track_system_variables
+character_set_client,example_int_var,myisam_sort_buffer_size
+set session example_int_var = -1;
+-- Tracker : SESSION_TRACK_SYSTEM_VARIABLES
+-- example_int_var: -1
+
+connection default;
+disconnect foo;
+uninstall soname 'ha_example.so';
+SET @@global.session_track_system_variables = @global_saved_tmp;
+# End of 10.11 tests

mysql-test/suite/sys_vars/t/session_track_system_variables_basic.test

@@ -126,3 +126,33 @@ SET SESSION session_track_system_variables="sql_slave_skip_counter", sql_slave_s
 SET @@global.session_track_system_variables = @global_saved_tmp;
 
 --echo # End of tests.
+
+--echo #
+--echo # MDEV-39207 plugin variables disappear from session_track_system_variables list
+--echo #
+
+install soname 'ha_example.so';
+
+--echo # Plugin global vars are not included
+set global session_track_system_variables='myisam_block_size';
+select @@global.session_track_system_variables;
+set global session_track_system_variables='example_int_var';
+select @@global.session_track_system_variables;
+set global session_track_system_variables='myisam_sort_buffer_size,example_int_var';
+select @@global.session_track_system_variables;
+set global session_track_system_variables='myisam_block_size,myisam_sort_buffer_size,character_set_client,example_int_var';
+select @@global.session_track_system_variables;
+
+--echo # Session tracking works as expected for plugin session var
+connect foo,localhost,root;
+enable_session_track_info;
+select @@session.session_track_system_variables;
+set session example_int_var = -1;
+disable_session_track_info;
+
+connection default;
+disconnect foo;
+uninstall soname 'ha_example.so';
+SET @@global.session_track_system_variables = @global_saved_tmp;
+
+--echo # End of 10.11 tests

sql/session_tracker.cc

@@ -329,7 +329,9 @@ bool Session_sysvars_tracker::vars_list::construct_var_list(char *buf,
   }
   mysql_mutex_unlock(&LOCK_plugin);
 
-  buf--; buf[0]= '\0';
+  if (idx > 0)
+    buf--;
+  buf[0]= '\0';
   my_safe_afree(names, names_size);
 
   return false;

sql/sql_plugin.cc

@@ -4212,9 +4212,14 @@ static int test_plugin_options(MEM_ROOT *tmp_root, struct st_plugin_int *tmp,
   struct st_bookmark *var;
   size_t len=0, count= EXTRA_OPTIONS;
   st_ptr_backup *tmp_backup= 0;
+  const char *plugin_name= tmp->plugin->name;
+  size_t plugin_name_len= strlen(plugin_name);
   DBUG_ENTER("test_plugin_options");
   DBUG_ASSERT(tmp->plugin && tmp->name.str);
 
+  char *plugin_name_ptr= static_cast<char*>(alloc_root(mem_root, plugin_name_len + 1));
+  safe_strcpy(plugin_name_ptr, plugin_name_len + 1, plugin_name);
+  my_casedn_str(&my_charset_latin1, plugin_name_ptr);
   if (tmp->plugin->system_vars || (*argc > 1))
   {
     for (opt= tmp->plugin->system_vars; opt && *opt; opt++)
@@ -4250,7 +4255,7 @@ static int test_plugin_options(MEM_ROOT *tmp_root, struct st_plugin_int *tmp,
         sys_var *v;
 
         tmp_backup[tmp->nbackups++].save(&o->name);
-        if ((var= find_bookmark(tmp->name.str, o->name, o->flags)))
+        if ((var= find_bookmark(plugin_name_ptr, o->name, o->flags)))
         {
           varname= var->key + 1;
           var->loaded= TRUE;