Backport into build-201102032246-5.1.52sp1

> ------------------------------------------------------------
> revno: 3452.13.54
> revision-id: oystein.grovlen@oracle.com-20110112093715-tc076voaxwblqk8v
> parent: georgi.kodinov@oracle.com-20110110130833-1c9q21mr7zoq07vg
> committer: Oystein Grovlen <oystein.grovlen@oracle.com>
> branch nick: mysql-5.1-security
> timestamp: Wed 2011-01-12 10:37:15 +0100
> message:
>   Bug#59211: Select Returns Different Value for min(year) Function
>   
>   get_year_value() contains code to convert 2-digits year to
>   4-digits.  The fix for Bug#49910 added a check on the size of
>   the underlying field so that this conversion is not done for
>   YEAR(4) values. (Since otherwise one would convert invalid
>   YEAR(4) values to valid ones.)
>   
>   The existing check does not work when Item_cache is used, since
>   it is not detected when the cache is based on a Field.  The
>   reported change in behavior is due to Bug#58030 which added
>   extra cached items in min/max computations.
>   
>   The elegant solution would be to implement
>   Item_cache::real_item() to return the underlying Item.
>   However, some side effects are observed (change in explain
>   output) that indicates that such a change is not straight-
>   forward, and definitely not appropriate for an MRU.
>   
>   Instead, a Item_cache::field() method has been added in order
>   to get access to the underlying field.  (This field() method
>   eliminates the need for Item_cache::eq_def() used in
>   test_if_ref(), but in order to limit the scope of this fix,
>   that code has been left as is.)

mysql-test/r/type_year.result

@@ -341,4 +341,18 @@ ta_y	s	tb_y	s
 2001	2001	2001	2001
 DROP TABLE t1;
 #
+# Bug #59211: Select Returns Different Value for min(year) Function
+#
+CREATE TABLE t1(c1 YEAR(4));
+INSERT INTO t1 VALUES (1901),(2155),(0000);
+SELECT * FROM t1;
+c1
+1901
+2155
+0000
+SELECT COUNT(*) AS total_rows, MIN(c1) AS min_value, MAX(c1) FROM t1;
+total_rows	min_value	MAX(c1)
+3	0	2155
+DROP TABLE t1;
+#
 End of 5.1 tests

mysql-test/t/type_year.test

@@ -149,6 +149,16 @@ SELECT ta.y AS ta_y, ta.s, tb.y AS tb_y, tb.s FROM t1 ta, t1 tb HAVING ta_y = tb
 
 DROP TABLE t1;
 
+--echo #
+--echo # Bug #59211: Select Returns Different Value for min(year) Function
+--echo #
+
+CREATE TABLE t1(c1 YEAR(4));
+INSERT INTO t1 VALUES (1901),(2155),(0000);
+SELECT * FROM t1;
+SELECT COUNT(*) AS total_rows, MIN(c1) AS min_value, MAX(c1) FROM t1;
+DROP TABLE t1;
+
 --echo #
 
 --echo End of 5.1 tests

sql/item.h

@@ -2960,11 +2960,10 @@ class Item_cache: public Item_basic_constant
 protected:
   Item *example;
   table_map used_table_map;
-  /*
-    Field that this object will get value from. This is set/used by 
+  /**
+    Field that this object will get value from. This is used by 
     index-based subquery engines to detect and remove the equality injected 
     by IN->EXISTS transformation.
-    For all other uses of Item_cache, cached_field doesn't matter.
   */  
   Field *cached_field;
   enum enum_field_types cached_field_type;
@@ -3021,6 +3020,14 @@ public:
   {
     return this == item;
   }
+
+  /** 
+    If this item caches a field value, return pointer to underlying field.
+
+    @return Pointer to field, or NULL if this is not a cache for a field value.
+  */
+  Field* field() { return cached_field; }
+
   virtual void store(Item *item);
   virtual bool cache_value()= 0;
 };

sql/item_cmpfunc.cc

@@ -1196,9 +1196,12 @@ get_year_value(THD *thd, Item ***item_arg, Item **cache_arg,
          value of 2000.
   */
   Item *real_item= item->real_item();
-  if (!(real_item->type() == Item::FIELD_ITEM &&
-        ((Item_field *)real_item)->field->type() == MYSQL_TYPE_YEAR &&
-        ((Item_field *)real_item)->field->field_length == 4))
+  Field *field= NULL;
+  if (real_item->type() == Item::FIELD_ITEM)
+    field= ((Item_field *)real_item)->field;
+  else if (real_item->type() == Item::CACHE_ITEM)
+    field= ((Item_cache *)real_item)->field();
+  if (!(field && field->type() == MYSQL_TYPE_YEAR && field->field_length == 4))
   {
     if (value < 70)
       value+= 100;