This is the consolidated patch for mdev-8646:bb-10.2-mdev8646

"Re-factor the code for post-join operations".

The patch mainly contains the code ported from mysql-5.6 and
created for two essential architectural changes:
1. WL#5558: Resolve ORDER BY execution method at the optimization stage
2. WL#6071: Inline tmp tables into the nested loops algorithm

The first task was implemented for mysql-5.6 by Ole John Aske.
It allows to make all decisions on ORDER BY operation at the optimization
stage.

The second task implemented for mysql-5.6 by Evgeny Potemkin adds JOIN_TAB
nodes for post-join operations that require temporary tables. It allows
to execute these operations within the nested loops algorithm that used to
be used before this task only for join queries. Besides these task moves
all planning on the execution of these operations from the execution phase
to the optimization phase.

Some other re-factoring changes of mysql-5.6 were pulled in, mainly because
it was easier to pull them in than roll them back. In particular all
changes concerning Ref_ptr_array were incorporated.

The port required some changes in the MariaDB code that concerned the
functionality of EXPLAIN and ANALYZE. This was done mainly by Sergey
Petrunia.

1 files changed, 10 insertions, 3 deletions

diff --git a/sql/item_func.cc b/sql/item_func.cc
index 4b376706500..152ee9fc8f6 100644
--- a/sql/item_func.cc
+++ b/sql/item_func.cc
@@ -431,7 +431,7 @@ void Item_args::propagate_equal_fields(THD *thd,
   See comments in Item_cond::split_sum_func()
 */
 
-void Item_func::split_sum_func(THD *thd, Item **ref_pointer_array,
+void Item_func::split_sum_func(THD *thd,  Ref_ptr_array ref_pointer_array,
                                List<Item> &fields, uint flags)
 {
   Item **arg, **arg_end;
@@ -4902,9 +4902,16 @@ Item_func_set_user_var::update_hash(void *ptr, uint length,
     If we set a variable explicitely to NULL then keep the old
     result type of the variable
   */
-  if ((null_value= args[0]->null_value) && null_item)
+  if (args[0]->type() == Item::FIELD_ITEM)
+  {
+    /* args[0]->null_value may be outdated */
+    null_value= ((Item_field*)args[0])->field->is_null();
+  }
+  else
+    null_value= args[0]->null_value;
+  if (null_value && null_item)
     res_type= m_var_entry->type;                 // Don't change type of item
-  if (::update_hash(m_var_entry, (null_value= args[0]->null_value),
+  if (::update_hash(m_var_entry, null_value,
                     ptr, length, res_type, cs, unsigned_arg))
   {
     null_value= 1;