keep old engine & JOIN if we changed subquery Item (Bug #3646)

mysql-test/r/subselect.result:
  ALL/ANY test
mysql-test/t/subselect.test:
  ALL/ANY test
sql/item_subselect.cc:
  keep old engine & JOIN if we changed subquery Item, which allow avoid second all SELECT items fix_fields call with pervios clean up (because of second setup_tables which remove table->key_use and maybe something else)
  keep list when we change Item in SELECT list
  processing inserted max/min function (now JOIN::prepare will be called only once)
  methods of changing item for subselect engines
sql/item_subselect.h:
  change item & results procedure
sql/item_sum.cc:
  Item_sum_hybrid::clear moved to .cc file (to keep .h clean and to make inserving/removing debug info easy)
sql/item_sum.h:
  Item_sum_hybrid::clear moved to .cc file (to keep .h clean and to make inserving/removing debug info easy)
sql/sql_lex.cc:
  note about new method
sql/sql_lex.h:
  method for changing result of UNION JOINs
sql/sql_select.cc:
  method for changing result in JOIN
sql/sql_select.h:
  method for changing result in JOIN
sql/sql_union.cc:
  method for changing result in JOIN

1 files changed, 8 insertions, 0 deletions

diff --git a/sql/item_sum.cc b/sql/item_sum.cc
index eac8d31b256..0c5b29fc069 100644
--- a/sql/item_sum.cc
+++ b/sql/item_sum.cc
@@ -502,6 +502,14 @@ void Item_sum_variance::update_field()
 
 /* min & max */
 
+void Item_sum_hybrid::clear()
+{
+  sum= 0.0;
+  sum_int= 0;
+  value.length(0);
+  null_value= 1;
+}
+
 double Item_sum_hybrid::val()
 {
   DBUG_ASSERT(fixed == 1);