Reuse THD for new user connections

- To ensure that mallocs are marked for the correct THD, even if it's
  allocated in another thread, I added the thread_id to the THD constructor
- Added st_my_thread_var to thr_lock_info_init() to avoid a call to my_thread_var
- Moved things from THD::THD() to THD::init()
- Moved some things to THD::cleanup()
- Added THD::free_connection() and THD::reset_for_reuse()
- Added THD to CONNECT::create_thd()
- Added THD::thread_dbug_id and st_my_thread_var->dbug_id. These are needed
  to ensure that we have a constant thread_id used for debugging with a THD,
  even if it changes thread_id (=connection_id)
- Set variables.pseudo_thread_id in constructor. Removed not needed sets.

1 files changed, 1 insertions, 1 deletions

diff --git a/sql/sql_plugin.cc b/sql/sql_plugin.cc
index f540c268923..848358e517a 100644
--- a/sql/sql_plugin.cc
+++ b/sql/sql_plugin.cc
@@ -1769,7 +1769,7 @@ static void plugin_load(MEM_ROOT *tmp_root)
   TABLE *table;
   READ_RECORD read_record_info;
   int error;
-  THD *new_thd= new THD;
+  THD *new_thd= new THD(0);
   bool result;
   DBUG_ENTER("plugin_load");