Clumsy but working fix for bug #11973 "SELECT .. INTO var_name; in trigger

cause crash on update".

Let us update "thd" pointer in LEX, all its units and in LEX::result before
executing statement in trigger body, since triggers are associated with TABLE
object and because of this can be used in different threads.

1 files changed, 5 insertions, 2 deletions

diff --git a/sql/item_subselect.h b/sql/item_subselect.h
index 0b5736169fa..46623f76170 100644
--- a/sql/item_subselect.h
+++ b/sql/item_subselect.h
@@ -299,8 +299,11 @@ public:
   virtual ~subselect_engine() {}; // to satisfy compiler
   virtual void cleanup()= 0;
 
-  // set_thd should be called before prepare()
-  void set_thd(THD *thd_arg) { thd= thd_arg; }
+  /*
+    Also sets "thd" for subselect_engine::result.
+    Should be called before prepare().
+  */
+  void set_thd(THD *thd_arg);
   THD * get_thd() { return thd; }
   virtual int prepare()= 0;
   virtual void fix_length_and_dec(Item_cache** row)= 0;