Simpler arena swapping code

Now thd->mem_root is a pointer to thd->main_mem_root and THR_MALLOC is a pointer to thd->mem_root.
This gives us the following benefits:
- Allow us to easily detect if arena has already been swapped before (this fixes a bug in setup_conds() where arena was swaped twice in some cases)
- Faster swaps of arenas (as we don't have to copy the whole MEM_ROOT)
- We don't anymore have to call my_pthread_setspecific_ptr(THR_MALLOC,...) to change where memory is alloced. Now it's enough to set thd->mem_root

1 files changed, 3 insertions, 3 deletions

diff --git a/sql/sql_error.cc b/sql/sql_error.cc
index 87644300535..eab5ec890df 100644
--- a/sql/sql_error.cc
+++ b/sql/sql_error.cc
@@ -113,12 +113,12 @@ MYSQL_ERROR *push_warning(THD *thd, MYSQL_ERROR::enum_warning_level level,
       The following code is here to change the allocation to not
       use the thd->mem_root, which is freed after each query
     */
-    MEM_ROOT *old_root=my_pthread_getspecific_ptr(MEM_ROOT*,THR_MALLOC);
-    my_pthread_setspecific_ptr(THR_MALLOC, &thd->warn_root);
+    MEM_ROOT *old_root= thd->mem_root;
+    thd->mem_root= &thd->warn_root;
     err= new MYSQL_ERROR(thd, code, level, msg);
     if (err)
       thd->warn_list.push_back(err);
-    my_pthread_setspecific_ptr(THR_MALLOC, old_root);
+    thd->mem_root= old_root;
   }
   thd->warn_count[(uint) level]++;
   thd->total_warn_count++;