Bug#43668: Wrong comparison and MIN/MAX for YEAR(2)

MySQL manual describes values of the YEAR(2) field type as follows:
values 00 - 69 mean 2000 - 2069 years and values 70 - 99 mean 1970 - 1999
years. MIN/MAX and comparison functions was comparing them as int values
thus producing wrong result.

Now the Arg_comparator class is extended with compare_year function which
performs correct comparison of the YEAR type.
The Item_sum_hybrid class now uses Item_cache and Arg_comparator objects to
correctly calculate its value.
To allow Arg_comparator to use func_name() function for Item_func and Item_sum
objects the func_name declaration is moved to the Item_result_field class.
A helper function is_owner_equal_func is added to the Arg_comparator class.
It checks whether the Arg_comparator object owner is the <=> function or not.
A helper function setup is added to the Item_sum_hybrid class. It sets up
cache item and comparator.

mysql-test/r/func_group.result:
  Added a test case for the bug#43668.
mysql-test/t/func_group.test:
  Added a test case for the bug#43668.
sql/item.cc:
  Bug#43668: Wrong comparison and MIN/MAX for YEAR(2)
  Now Item_cache_int returns the type of cached item.
sql/item.h:
  Bug#43668: Wrong comparison and MIN/MAX for YEAR(2)
  To allow Arg_comparator to use func_name() function for Item_func and Item_sum
  objects the func_name declaration is moved to the Item_result_field class.
sql/item_cmpfunc.cc:
  Bug#43668: Wrong comparison and MIN/MAX for YEAR(2)
  The Arg_comparator class is extended with compare_year function which
  performs correct comparison of the YEAR type.
sql/item_cmpfunc.h:
  Bug#43668: Wrong comparison and MIN/MAX for YEAR(2)
  The year_as_datetime variable is added to the Arg_comparator class.
  It's set to TRUE when YEAR value should be converted to the
  YYYY-00-00 00:00:00 format for correct YEAR-DATETIME comparison.
sql/item_geofunc.cc:
  Bug#43668: Wrong comparison and MIN/MAX for YEAR(2)
  Item_func_spatial_rel::val_int chenged to use Arg_comparator's string
  buffers.
sql/item_subselect.h:
  Bug#43668: Wrong comparison and MIN/MAX for YEAR(2)
  Added an implementation of the virtual func_name function.
sql/item_sum.cc:
  Bug#43668: Wrong comparison and MIN/MAX for YEAR(2)
  The Item_sum_hybrid class now uses Item_cache and Arg_comparator objects to
  correctly calculate its value.
  A helper function setup is added to the Item_sum_hybrid class. It sets up
  cache item and comparator.
sql/item_sum.h:
  Bug#43668: Wrong comparison and MIN/MAX for YEAR(2)
  The Item_sum_hybrid class now uses Item_cache and Arg_comparator objects to
  correctly calculate its value.
  Added an implementation of the virtual func_name function.

1 files changed, 14 insertions, 23 deletions

diff --git a/sql/item_sum.h b/sql/item_sum.h
index d991327d847..f70da52bcd1 100644
--- a/sql/item_sum.h
+++ b/sql/item_sum.h
@@ -323,22 +323,6 @@ public:
   virtual void update_field()=0;
   virtual bool keep_field_type(void) const { return 0; }
   virtual void fix_length_and_dec() { maybe_null=1; null_value=1; }
-  /*
-    This method is used for debug purposes to print the name of an
-    item to the debug log. The second use of this method is as
-    a helper function of print(), where it is applicable.
-    To suit both goals it should return a meaningful,
-    distinguishable and sintactically correct string.  This method
-    should not be used for runtime type identification, use enum
-    {Sum}Functype and Item_func::functype()/Item_sum::sum_func()
-    instead.
-
-    NOTE: for Items inherited from Item_sum, func_name() return part of
-    function name till first argument (including '(') to make difference in
-    names for functions with 'distinct' clause and without 'distinct' and
-    also to make printing of items inherited from Item_sum uniform.
-  */
-  virtual const char *func_name() const= 0;
   virtual Item *result_item(Field *field)
     { return new Item_field(field); }
   table_map used_tables() const { return used_tables_cache; }
@@ -664,6 +648,7 @@ public:
   }
   void fix_length_and_dec() {}
   enum Item_result result_type () const { return hybrid_type; }
+  const char *func_name() const { DBUG_ASSERT(0); return "avg_field"; }
 };
 
 
@@ -732,6 +717,7 @@ public:
   }
   void fix_length_and_dec() {}
   enum Item_result result_type () const { return hybrid_type; }
+  const char *func_name() const { DBUG_ASSERT(0); return "variance_field"; }
 };
 
 
@@ -807,6 +793,7 @@ public:
   my_decimal *val_decimal(my_decimal *);
   enum Item_result result_type () const { return REAL_RESULT; }
   enum_field_types field_type() const { return MYSQL_TYPE_DOUBLE;}
+  const char *func_name() const { DBUG_ASSERT(0); return "std_field"; }
 };
 
 /*
@@ -832,14 +819,13 @@ class Item_sum_std :public Item_sum_variance
 };
 
 // This class is a string or number function depending on num_func
-
+class Arg_comparator;
+class Item_cache;
 class Item_sum_hybrid :public Item_sum
 {
 protected:
-  String value,tmp_value;
-  double sum;
-  longlong sum_int;
-  my_decimal sum_dec;
+  Item_cache *value;
+  Arg_comparator *cmp;
   Item_result hybrid_type;
   enum_field_types hybrid_field_type;
   int cmp_sign;
@@ -847,12 +833,17 @@ protected:
 
   public:
   Item_sum_hybrid(Item *item_par,int sign)
-    :Item_sum(item_par), sum(0.0), sum_int(0),
+    :Item_sum(item_par), value(0), cmp(0),
     hybrid_type(INT_RESULT), hybrid_field_type(MYSQL_TYPE_LONGLONG),
     cmp_sign(sign), was_values(TRUE)
   { collation.set(&my_charset_bin); }
-  Item_sum_hybrid(THD *thd, Item_sum_hybrid *item);
+  Item_sum_hybrid(THD *thd, Item_sum_hybrid *item)
+    :Item_sum(thd, item), value(item->value), hybrid_type(item->hybrid_type),
+    hybrid_field_type(item->hybrid_field_type), cmp_sign(item->cmp_sign),
+    was_values(item->was_values)
+  { }
   bool fix_fields(THD *, Item **);
+  void setup(Item *item, Item *value_arg);
   void clear();
   double val_real();
   longlong val_int();