Fix for LP#612894 Some aggregate functions (such as MIN MAX) work incorrectly in subqueries after getting NULL value

mysql-test/r/group_by.result:
  Added test that showed problems that no_rows_in_results() didn't work for expressions
mysql-test/r/subselect4.result:
  Test case for LP#612894
mysql-test/t/group_by.test:
  Added test that showed problems that no_rows_in_results() didn't work for expressions
mysql-test/t/subselect4.test:
  Test case for LP#612894
sql/item.h:
  Added restore_to_before_no_rows_in_result()
  Added function processor for no_rows_in_results() and restore_to_before_no_rows_in_results() to ensure it works with functions
  Fix that above functions are handled by Item_ref()
sql/item_func.h:
  Ensure that no_rows_in_results() and restore_to_before_no_rows_in_result() are called for all function arguments
sql/item_sum.cc:
  Added restore_to_before_no_rows_in_result() to restore settings after Item_sum_hybrid::no_rows_in_result() was called.
  This is needed to handle the case where we have made 'make_const()' on the item in opt_sum(), but the item will be reused again in a sub query.
  Ignore multiple calls to no_rows_in_result() as Item_ref is calling it twice.
sql/item_sum.h:
  Added restore_to_before_no_rows_in_result();
sql/sql_select.cc:
  Added reset of no_rows_in_result() for JOIN::reinit()
sql/sql_select.h:
  Added marker if no_rows_in_result() is called.

1 files changed, 3 insertions, 1 deletions

diff --git a/sql/item_sum.h b/sql/item_sum.h
index b82f2d961f1..ac6a56400a4 100644
--- a/sql/item_sum.h
+++ b/sql/item_sum.h
@@ -496,7 +496,7 @@ public:
   enum Sumfunctype sum_func () const { return SUM_DISTINCT_FUNC; }
   void reset_field() {} // not used
   void update_field() {} // not used
-  virtual void no_rows_in_result() {}
+  void no_rows_in_result() {}
   void fix_length_and_dec();
   enum Item_result result_type () const { return val.traits->type(); }
   virtual void calculate_val_and_count();
@@ -845,6 +845,7 @@ protected:
   enum_field_types hybrid_field_type;
   int cmp_sign;
   bool was_values;  // Set if we have found at least one row (for max/min only)
+  bool was_null_value;
 
   public:
   Item_sum_hybrid(Item *item_par,int sign)
@@ -876,6 +877,7 @@ protected:
   void cleanup();
   bool any_value() { return was_values; }
   void no_rows_in_result();
+  void restore_to_before_no_rows_in_result();
   Field *create_tmp_field(bool group, TABLE *table,
 			  uint convert_blob_length);
 };