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, 6 insertions, 4 deletions

diff --git a/sql/ha_berkeley.cc b/sql/ha_berkeley.cc
index 09b3e340d1f..2c7cce4bcd0 100644
--- a/sql/ha_berkeley.cc
+++ b/sql/ha_berkeley.cc
@@ -234,13 +234,13 @@ int berkeley_show_logs(Protocol *protocol)
 {
   char **all_logs, **free_logs, **a, **f;
   int error=1;
-  MEM_ROOT show_logs_root;
-  MEM_ROOT *old_root=my_pthread_getspecific_ptr(MEM_ROOT*,THR_MALLOC);
+  MEM_ROOT **root_ptr= my_pthread_getspecific_ptr(MEM_ROOT**,THR_MALLOC);
+  MEM_ROOT show_logs_root, *old_mem_root= *root_ptr;
   DBUG_ENTER("berkeley_show_logs");
 
   init_sql_alloc(&show_logs_root, BDB_LOG_ALLOC_BLOCK_SIZE,
 		 BDB_LOG_ALLOC_BLOCK_SIZE);
-  my_pthread_setspecific_ptr(THR_MALLOC,&show_logs_root);
+  *root_ptr= &show_logs_root;
 
   if ((error= db_env->log_archive(db_env, &all_logs,
 				  DB_ARCH_ABS | DB_ARCH_LOG)) ||
@@ -277,15 +277,17 @@ int berkeley_show_logs(Protocol *protocol)
   }
 err:
   free_root(&show_logs_root,MYF(0));
-  my_pthread_setspecific_ptr(THR_MALLOC,old_root);
+  *root_ptr= old_mem_root;
   DBUG_RETURN(error);
 }
 
+
 static void berkeley_print_error(const char *db_errpfx, char *buffer)
 {
   sql_print_error("%s:  %s",db_errpfx,buffer); /* purecov: tested */
 }
 
+
 static void berkeley_noticecall(DB_ENV *db_env, db_notices notice)
 {
   switch (notice)