- a fix for Bug#11458 "Prepared statement with subselects return random

data": remove the fix for another bug (8807) that
added OUTER_REF_TABLE_BIT to all subqueries that used a placeholder
to prevent their evaluation at prepare. As this bit hanged in 
Item_subselect::used_tables_cache for ever, a constant subquery with
a placeholder was never evaluated as such, which caused wrong 
choice of the execution plan for the statement.
- to fix Bug#8807 backport a better fix from 5.0
- post-review fixes.


mysql-test/r/ps.result:
  Bug#11458: test results fixed
mysql-test/t/ps.test:
  - add a test case for Bug#11458 "Prepared statement with subselects return 
  random data"
sql/item.cc:
  - remove unnecessary Item_param::fix_fields
  - fix Item_param::set_null to set item_type accordingly (safety:
    Item_param should behave like a basic constant).
sql/item.h:
  Remove Item_param::fix_fields
sql/item_subselect.h:
  Remove no more existing friend.
sql/mysql_priv.h:
  Add UNCACHEABLE_PREPARE to mark all subqueries as uncacheable if
  in statement prepare (backport from 5.0).
sql/sql_lex.h:
  Comment fixed.
sql/sql_parse.cc:
  If in statement prepare, mark all subqueries as uncacheable (backport
  from 5.0)
sql/sql_prepare.cc:
  Switch off the uncacheable flag from all subqueries after statement
  prepare is done (backport from 5.0)

1 files changed, 1 insertions, 28 deletions

diff --git a/sql/item.cc b/sql/item.cc
index 3bdaf856f2a..19b88c115b9 100644
--- a/sql/item.cc
+++ b/sql/item.cc
@@ -889,6 +889,7 @@ void Item_param::set_null()
   max_length= 0;
   decimals= 0;
   state= NULL_VALUE;
+  item_type= Item::NULL_ITEM;
   DBUG_VOID_RETURN;
 }
 
@@ -1339,34 +1340,6 @@ bool Item_param::convert_str_value(THD *thd)
   return rc;
 }
 
-bool Item_param::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
-{
-  DBUG_ASSERT(fixed == 0);
-  SELECT_LEX *cursel= (SELECT_LEX *) thd->lex->current_select;
-
-  /*
-    Parameters in a subselect should mark the subselect as not constant
-    during prepare
-  */
-  if (state == NO_VALUE)
-  {
-    /*
-      SELECT_LEX_UNIT::item set only for subqueries, so test of it presence
-      can be barrier to stop before derived table SELECT or very outer SELECT
-    */
-    for(;
-        cursel->master_unit()->item;
-        cursel= cursel->outer_select())
-    {
-      Item_subselect *subselect_item= cursel->master_unit()->item;
-      subselect_item->used_tables_cache|= OUTER_REF_TABLE_BIT;
-      subselect_item->const_item_cache= 0;
-    }
-  }
-  fixed= 1;
-  return 0;
-}
-
 
 bool Item_param::basic_const_item() const
 {