Bug #49480: WHERE using YEAR columns returns unexpected results

A few problems were found in the fix for bug 43668:
1) Comparison of the YEAR column with NULL always returned TRUE;
2) Comparison of the YEAR column with constants always returned
   unpredictable result;
3) Unnecessary conversion warnings when comparing a non-integer
   constant with a NULL value in the YEAR column;

The problems described above have been resolved with an
exception: zero (i.e. invalid) YEAR column value comparison
with 00 or 2000 still fail (it is not a regression and it was
not a regression), so MIN/MAX on YEAR column containing zero
value still fail.

1 files changed, 3 insertions, 6 deletions

diff --git a/sql/item_cmpfunc.h b/sql/item_cmpfunc.h
index 52af6a31c0c..d4542dac820 100644
--- a/sql/item_cmpfunc.h
+++ b/sql/item_cmpfunc.h
@@ -42,24 +42,22 @@ class Arg_comparator: public Sql_alloc
   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_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);
+  bool try_year_cmp_func(Item_result type);
 public:
   DTCollation cmp_collation;
   /* Allow owner function to use string buffers. */
   String value1, value2;
 
   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) {};
+    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), set_null(0), year_as_datetime(0),
+    a_cache(0), b_cache(0), set_null(0),
     get_value_a_func(0), get_value_b_func(0) {};
 
   int set_compare_func(Item_result_field *owner, Item_result type);
@@ -101,7 +99,6 @@ 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);