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, 30 insertions, 13 deletions

diff --git a/sql/item_cmpfunc.h b/sql/item_cmpfunc.h
index c2227fa04e0..3cf4a1473cc 100644
--- a/sql/item_cmpfunc.h
+++ b/sql/item_cmpfunc.h
@@ -32,7 +32,7 @@ class Arg_comparator: public Sql_alloc
 {
   Item **a, **b;
   arg_cmp_func func;
-  Item_bool_func2 *owner;
+  Item_result_field *owner;
   Arg_comparator *comparators;   // used only for compare_row()
   double precision;
   /* Fields used in DATE/DATETIME comparison. */
@@ -40,30 +40,42 @@ class Arg_comparator: public Sql_alloc
   enum_field_types a_type, b_type; // Types of a and b items
   Item *a_cache, *b_cache;         // Cached values of a and b items
   bool is_nulls_eq;                // TRUE <=> compare for the EQUAL_FUNC
+  bool set_null;                   // TRUE <=> set owner->null_value
+                                   //   when one of arguments is NULL.
+  bool year_as_datetime;           // TRUE <=> convert YEAR value to
+                                   // the YYYY-00-00 00:00:00 DATETIME
+                                   // format. See compare_year.
   enum enum_date_cmp_type { CMP_DATE_DFLT= 0, CMP_DATE_WITH_DATE,
                             CMP_DATE_WITH_STR, CMP_STR_WITH_DATE };
-  longlong (*get_value_func)(THD *thd, Item ***item_arg, Item **cache_arg,
-                             Item *warn_item, bool *is_null);
+  longlong (*get_value_a_func)(THD *thd, Item ***item_arg, Item **cache_arg,
+                               Item *warn_item, bool *is_null);
+  longlong (*get_value_b_func)(THD *thd, Item ***item_arg, Item **cache_arg,
+                               Item *warn_item, bool *is_null);
 public:
   DTCollation cmp_collation;
+  /* Allow owner function to use string buffers. */
+  String value1, value2;
 
-  Arg_comparator(): thd(0), a_cache(0), b_cache(0) {};
+  Arg_comparator(): thd(0), a_cache(0), b_cache(0), set_null(0),
+    year_as_datetime(0), get_value_a_func(0), get_value_b_func(0) {};
   Arg_comparator(Item **a1, Item **a2): a(a1), b(a2), thd(0),
-    a_cache(0), b_cache(0) {};
+    a_cache(0), b_cache(0), set_null(0), year_as_datetime(0),
+    get_value_a_func(0), get_value_b_func(0) {};
 
-  int set_compare_func(Item_bool_func2 *owner, Item_result type);
-  inline int set_compare_func(Item_bool_func2 *owner_arg)
+  int set_compare_func(Item_result_field *owner, Item_result type);
+  inline int set_compare_func(Item_result_field *owner_arg)
   {
     return set_compare_func(owner_arg, item_cmp_type((*a)->result_type(),
                                                      (*b)->result_type()));
   }
-  int set_cmp_func(Item_bool_func2 *owner_arg,
+  int set_cmp_func(Item_result_field *owner_arg,
 			  Item **a1, Item **a2,
 			  Item_result type);
 
-  inline int set_cmp_func(Item_bool_func2 *owner_arg,
-			  Item **a1, Item **a2)
+  inline int set_cmp_func(Item_result_field *owner_arg,
+			  Item **a1, Item **a2, bool set_null_arg)
   {
+    set_null= set_null_arg;
     return set_cmp_func(owner_arg, a1, a2,
                         item_cmp_type((*a1)->result_type(),
                                       (*a2)->result_type()));
@@ -89,12 +101,18 @@ public:
   int compare_real_fixed();
   int compare_e_real_fixed();
   int compare_datetime();        // compare args[0] & args[1] as DATETIMEs
+  int compare_year();
 
   static enum enum_date_cmp_type can_compare_as_dates(Item *a, Item *b,
                                                       ulonglong *const_val_arg);
 
-  void set_datetime_cmp_func(Item **a1, Item **b1);
+  void set_datetime_cmp_func(Item_result_field *owner_arg, Item **a1, Item **b1);
   static arg_cmp_func comparator_matrix [5][2];
+  inline bool is_owner_equal_func()
+  {
+    return (owner->type() == Item::FUNC_ITEM &&
+           ((Item_func*)owner)->functype() == Item_func::EQUAL_FUNC);
+  }
 
   friend class Item_func;
 };
@@ -324,7 +342,6 @@ class Item_bool_func2 :public Item_int_func
 {						/* Bool with 2 string args */
 protected:
   Arg_comparator cmp;
-  String tmp_value1,tmp_value2;
   bool abort_on_null;
 
 public:
@@ -333,7 +350,7 @@ public:
   void fix_length_and_dec();
   void set_cmp_func()
   {
-    cmp.set_cmp_func(this, tmp_arg, tmp_arg+1);
+    cmp.set_cmp_func(this, tmp_arg, tmp_arg+1, TRUE);
   }
   optimize_type select_optimize() const { return OPTIMIZE_OP; }
   virtual enum Functype rev_functype() const { return UNKNOWN_FUNC; }