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.

2 files changed, 4 insertions, 4 deletions

diff --git a/plugin/feedback/sender_thread.cc b/plugin/feedback/sender_thread.cc
index f7b9f440fcd..1b90d2cb340 100644
--- a/plugin/feedback/sender_thread.cc
+++ b/plugin/feedback/sender_thread.cc
@@ -89,7 +89,7 @@ static int prepare_for_fill(TABLE_LIST *tables)
     (every increment of global thread_id counts as a new connection
     in SHOW STATUS and we want to avoid skewing the statistics)
   */
-  thd->thread_id= thd->variables.pseudo_thread_id= thd_thread_id;
+  thd->variables.pseudo_thread_id= thd->thread_id;
   mysql_mutex_lock(&LOCK_thread_count);
   thread_count++;
   threads.append(thd);
@@ -205,10 +205,10 @@ static void send_report(const char *when)
     /*
       otherwise, prepare the THD and TABLE_LIST,
       create and fill the temporary table with data just like
-      SELECT * FROM IFROEMATION_SCHEMA.feedback is doing,
+      SELECT * FROM INFORMATION_SCHEMA.feedback is doing,
       read and concatenate table data into a String.
     */
-    if (!(thd= new THD()))
+    if (!(thd= new THD(thd_thread_id)))
       return;
 
     if (prepare_for_fill(&tables))
diff --git a/plugin/handler_socket/handlersocket/database.cpp b/plugin/handler_socket/handlersocket/database.cpp
index 94eedbf6d04..28ce6c78876 100644
--- a/plugin/handler_socket/handlersocket/database.cpp
+++ b/plugin/handler_socket/handlersocket/database.cpp
@@ -278,7 +278,7 @@ dbcontext::init_thread(const void *stack_bottom, volatile int& shutdown_flag)
   DBG_THR(fprintf(stderr, "HNDSOCK init thread\n"));
   {
     my_thread_init();
-    thd = new THD;
+    thd = new THD(0);
     thd->thread_stack = (char *)stack_bottom;
     DBG_THR(fprintf(stderr,
       "thread_stack = %p sizeof(THD)=%zu sizeof(mtx)=%zu "