MDEV-6858: enforce_storage_engine option

Merge from Percona Server enforced use of a specific storage engine
authored by Stewart Smith.

Modified to be session variable and modifiable only by SUPER. Use
similar implementation as default_storage_engine.

1 files changed, 7 insertions, 1 deletions

diff --git a/sql/sql_plugin.cc b/sql/sql_plugin.cc
index 2fe22ea5d43..fe020d36f93 100644
--- a/sql/sql_plugin.cc
+++ b/sql/sql_plugin.cc
@@ -3089,11 +3089,13 @@ void plugin_thdvar_init(THD *thd)
 {
   plugin_ref old_table_plugin= thd->variables.table_plugin;
   plugin_ref old_tmp_table_plugin= thd->variables.tmp_table_plugin;
+  plugin_ref old_enforced_table_plugin= thd->variables.enforced_table_plugin;
   DBUG_ENTER("plugin_thdvar_init");
 
   // This function may be called many times per THD (e.g. on COM_CHANGE_USER)
   thd->variables.table_plugin= NULL;
   thd->variables.tmp_table_plugin= NULL;
+  thd->variables.enforced_table_plugin= NULL;
   cleanup_variables(&thd->variables);
 
   thd->variables= global_system_variables;
@@ -3113,12 +3115,14 @@ void plugin_thdvar_init(THD *thd)
             intern_plugin_lock(NULL, global_system_variables.tmp_table_plugin);
     intern_plugin_unlock(NULL, old_table_plugin);
     intern_plugin_unlock(NULL, old_tmp_table_plugin);
+    intern_plugin_unlock(NULL, old_enforced_table_plugin);
     mysql_mutex_unlock(&LOCK_plugin);
   }
   else
   {
     thd->variables.table_plugin= NULL;
     thd->variables.tmp_table_plugin= NULL;
+    thd->variables.enforced_table_plugin= NULL;
   }
 
   DBUG_VOID_RETURN;
@@ -3132,7 +3136,8 @@ static void unlock_variables(THD *thd, struct system_variables *vars)
 {
   intern_plugin_unlock(NULL, vars->table_plugin);
   intern_plugin_unlock(NULL, vars->tmp_table_plugin);
-  vars->table_plugin= vars->tmp_table_plugin= NULL;
+  intern_plugin_unlock(NULL, vars->enforced_table_plugin);
+  vars->table_plugin= vars->tmp_table_plugin= vars->enforced_table_plugin= NULL;
 }
 
 
@@ -3170,6 +3175,7 @@ static void cleanup_variables(struct system_variables *vars)
 
   DBUG_ASSERT(vars->table_plugin == NULL);
   DBUG_ASSERT(vars->tmp_table_plugin == NULL);
+  DBUG_ASSERT(vars->enforced_table_plugin == NULL);
 
   my_free(vars->dynamic_variables_ptr);
   vars->dynamic_variables_ptr= NULL;