MDEV-14551 Can't find record in table on multi-table update with ORDER BY

preserve positions if the multi-update join is using tmp table:

* store positions in the tmp table if needed
  JOIN::add_fields_for_current_rowid()

* take positions from the tmp table, not from file->position():
  multi_update::prepare2()

1 files changed, 4 insertions, 3 deletions

diff --git a/sql/sql_class.h b/sql/sql_class.h
index bba1740b46f..0ff588a6d38 100644
--- a/sql/sql_class.h
+++ b/sql/sql_class.h
@@ -4981,7 +4981,7 @@ public:
     unit= u;
     return 0;
   }
-  virtual int prepare2(void) { return 0; }
+  virtual int prepare2(JOIN *join) { return 0; }
   /*
     Because of peculiarities of prepared statements protocol
     we need to know number of columns in the result set (if
@@ -5225,7 +5225,7 @@ class select_insert :public select_result_interceptor {
 		enum_duplicates duplic, bool ignore);
   ~select_insert();
   int prepare(List<Item> &list, SELECT_LEX_UNIT *u);
-  virtual int prepare2(void);
+  virtual int prepare2(JOIN *join);
   virtual int send_data(List<Item> &items);
   virtual void store_values(List<Item> &values);
   virtual bool can_rollback_data() { return 0; }
@@ -5277,7 +5277,7 @@ public:
   // Needed for access from local class MY_HOOKS in prepare(), since thd is proteted.
   const THD *get_thd(void) { return thd; }
   const HA_CREATE_INFO *get_create_info() { return create_info; };
-  int prepare2(void) { return 0; }
+  int prepare2(JOIN *join) { return 0; }
 
 private:
   TABLE *create_table_from_items(THD *thd,
@@ -5961,6 +5961,7 @@ public:
   int prepare(List<Item> &list, SELECT_LEX_UNIT *u);
   int send_data(List<Item> &items);
   bool initialize_tables (JOIN *join);
+  int prepare2(JOIN *join);
   int  do_updates();
   bool send_eof();
   inline ha_rows num_found() const { return found; }